bài tập Toán lớp 10 của Tee Van

cho pt kx^2 - 2(k+1)x + k + 1 = 0 
tìm các giá trị của k để phương trình trên có ít nhất 1 nghiệm dương


với k=0 ta có: -2x+1=0 => x=1/2 (thỏa yêu cầu bài toán)

với k≠0, ta có:



Để phưong trình có nghiệm thì =>k-1

Khi phương trình có 2 nghiệm thì sẽ có 3 trừờng hợp:


1.   2 âm

2.   1 dương 1 âm  

3.   2 dương.

Ta thấy trừơng hợp 2, 3 đã thỏa ỵêu cầu của bài toán, ta chỉ cần xét truờng hợp 1.

Trừơng hợp 1 xãy ra khi:

Hệ BĐT trên vô nghiệm, vậy trừơng hợp 1 không xãy ra.

Kết luận, hệ có nghiệm dương với k-1.


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Fox Host: 'Do We Really Want Everybody Voting? I Don’t Think So!' (VIDEO)

"Do we really want everybody voting?" Tantaros said during a discussion of the issue. "I don’t think so!"
The "Outnumbered" crew was up in arms after Obama told a Cleveland audience that "it would be transformative if everybody voted."
"If you’re not engaged enough to vote, please don’t," co-host Melissa Francis said earlier in the segment. "Stay home."
Meanwhile, co-host Harris Faulkner argued that mandatory voting would be un-American because soldiers “fought for our right to decide for ourselves."
“I don’t understand where the President falls on this: Is he against freedom?" she asked.
Co-host Kirsten Powers confessed when she was younger and encountered unfamiliar ballot items, she would "randomly pick" what to vote for, before determining that "you shouldn’t be voting if you aren’t informed about everything you’re voting for."
She called Obama's comments "a little authoritarian."
Watch below via Fox News:

Fox Host: 'Do We Really Want Everybody Voting... bởi talkingpointsmemo

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Watch Santorum Respond To Question On 'Communist Dictator' Obama

"Why is the Congress rolling over and letting this communist dictator destroy my country?" she asked Santorum. "You all know what he is, and I know what he is. I want him out of the White House. He's not a citizen. He could have been removed a long time ago."
She later mentioned that "Obama tried to blow up a nuke in Charleston a few months ago."
Santorum appeared confused and uncomfortable throughout her question, and someone had to cut her off so that Santorum could respond.
"I’m not a sitting member of the Senate, so I’m not taking blame for any of that stuff," he began, before voicing his opposition to Obama's executive actions on immigration.
"You hit on one point that I absolutely agree: this is a complete lack of leadership," he said.
Santorum said that "the word 'tyrant' comes to mind and claimed that the Constitution is "unraveling."
Watch the clip via Right Wing Watch:

Watch Santorum Respond To Question On... bởi talkingpointsmemo

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Reagan Library Curator: Scott Walker Is More Reagan-y Than I Said

The potential 2016 presidential contender has always been fond of comparing himself to Reagan. Recently, he likened his push to limit public sector employee's collective bargaining rights to the late President's contentious air traffic controller union-busting in the 1980s. But his penchant for all things Reagan can also border on the superstitious: Walker drew attention to the fact that his 2012 recall election victory coincided with the anniversary of the former President's death, and that his own wedding anniversary falls on Reagan's birthday.
The governor shared the story about holding the Bible at a 2013 Reagan Day Dinner in Milwaukee, according to the magazine The Progressive. He recalled visiting with Nancy Reagan at her Bel Air home before a speaking engagement at the Reagan Library in November 2012, months after the governor survived a recall election.

Reagan Library Curator: Scott Walker Is More... bởi talkingpointsmemo
"One of the other great privileges I had -- that was unbeknownst to me that they had set up -- was we came around the corner on the tour, before I gave a speech in front of about a thousand people at the library,” Walker said. “The curator there had -- I see him and he's got white gloves and he's got something in his hand.”
“They brought over a pair of white gloves to me and they said, 'No one has touched this since President Reagan. It’s his mother's Bible that he took the oath of office on. Mrs. Reagan would like you to hold it and take a picture with it,’” he continued to applause.
The Progressive got in touch with Jennifer Torres, an artifacts curator at the library, to fact-check Walker’s account for a story published last week.
Torres told the magazine by email that Walker had actually been the one who requested to hold the Bible when he visited the library for his speech. The wording of her response also suggested that Walker had made the request prior to traveling to California for the engagement.
“We decided to remove the Bible the day Gov. Walker was in town to comply with his request, took the Bible back to collections after the photo, and re-installed it on exhibit a few days later,” she wrote.
Torres also told the magazine that many members of the library’s staff had come in contact with the Bible, contradicting Walker’s statement that a curator had told him he was the first person to hold it since Reagan himself.
But Torres recanted some of those statements Monday, after the Associated Press picked up on the conflicting accounts of Walker's visit.
While Torres said Walker's advance team did inquire about an opportunity for the governor to view the Bible, the governor was genuinely surprised when he got to hold it himself, according to the report.
"It was the Reagan Foundation's request to actually pull the Bible from the case and allow Gov. Walker to hold the Bible," Torres told the AP. "It was not Gov. Walker nor his team's idea to request that we remove it from the case or take a picture of the governor with it."
Whether Nancy Reagan gave library staff a direct order to remove the Bible for Walker’s visit is a murkier matter, however.
The Reagan Foundation is a non-profit established by the late President, while the library is a branch of the National Archives. A Reagan Foundation spokeswoman told the AP that Walker probably thought the former first lady had pulled strings for him because her chief of staff had to give permission for the Bible to be removed from its display.
"She knew Mrs. Reagan would also like the idea and we shared that with him," spokeswoman Melissa Giller told the AP in an email. "We aren't sure how the other story got out (that it was his idea), and we feel badly about it because nothing about it was his idea."
Torres had sent an email to Giller explaining that the whole dispute had been a "simple misunderstanding," according to the AP.
Walker's political organization, Our American Renewal, has refrained from getting into the particulars of Walker's visit.
"Gov. Walker was honored to speak at the Reagan Library and to hold his mother's Bible," Walker spokeswoman Kirsten Kukowski told the AP. "He was and continues to be one of his heroes, a president for the ages that accomplished great things for our country."

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Dems On A Possible Trump 2016 Run: Everything Is Awesome!

In response to Trump's statement on Wednesday that he's planning on forming a presidential exploratory committee, DNC National Press Secretary Holly Shulman released a short statement that said "everything is awesome" with a link to the song in The Lego Movie:
Trump has repeatedly toyed with running for president before bowing out. He strongly floated running for president in 2012 as a Republican candidate before opting against it. He also dipped his toe into running in 2000, as an Independent candidate. Bloomberg Politics noted that in 2014, Trump also flirted with a possible gubernatorial run. That lasted three months before Trump opted against it.

Dems On A Possible Trump 2016 Run: Everything... bởi talkingpointsmemo

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Tattooed Neo-Nazi Named As Suspect In Deadly Arizona Shooting Spree

Following a manhunt that lasted hours, police took into custody a gunman who allegedly killed one person and wounded five others across multiple shooting scenes.
The Mesa Police Department has not released the suspect's name. But the Arizona Republic reported that anonymous police sources identified Ryan Eliot Giroux, 41, as the suspect in the shooting.

Tattooed Neo-Nazi Named As Suspect In Deadly... bởi talkingpointsmemo
Giroux was released from prison in 2013 after serving more than six years for attempted aggravated assault, according to records from the Arizona Department of Corrections. He had served two prior prison terms on burglary and marijuana charges.
Giroux also sports multiple face and neck tattoos, including eyebrow ink that reads "Skinhead" and an "88" on his left temple. The number is a code used for the Nazi salute "heil Hitler." In a news conference Wednesday, a spokesman for the Mesa Police Department described the suspect as a bald man with face and neck tattoos.
Retired Mesa Police Det. Matt Browning on Wednesday told the Southern Poverty Law Center's Hatewatch blog that he was familiar with Giroux. Browning identified Giroux as a member of the Hammerskin Nation, a racist skinhead group formed in the late 1980s.
Wade Page, the gunman in the 2012 Wisconsin Sikh temple shooting, had notably belonged to the same group.
Browning told Hatewatch that Giroux was also affiliated with the Aryan Brotherhood, a white supremacist prison gang that dates back to the 1960s.

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