摘要:y1+y2=2(k2+b).则 y1y2=b2. 方法一:
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(2008•浦东新区二模)问题:过点M(2,1)作一斜率为1的直线交抛物线y2=2px(p>0)于不同的两点A,B,且点M为AB的中点,求p的值.请阅读某同学的问题解答过程:
解:设A(x1,y1),B(x2,y2),则y12=2px1,y22=2px2,两式相减,得(y1-y2)(y1+y2)=2p(x1-x2).又kAB=
=1,y1+y2=2,因此p=1.
并给出当点M的坐标改为(2,m)(m>0)时,你认为正确的结论:
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解:设A(x1,y1),B(x2,y2),则y12=2px1,y22=2px2,两式相减,得(y1-y2)(y1+y2)=2p(x1-x2).又kAB=
| y1-y2 | x1-x2 |
并给出当点M的坐标改为(2,m)(m>0)时,你认为正确的结论:
p=m(0<m<4)
p=m(0<m<4)
.
已知数列{xn},{yn}满足x1=x2=1,y1=y2=2,并且
=λ
,
≥λ
(λ为非零参数,n=2,3,4,…).
(1)若x1,x3,x5成等比数列,求参数λ的值;
(2)当λ>0时,证明
≤
(n∈N*);当λ>1时,证明:
+
+…+
<
(n∈N*).
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| xn+1 |
| xn |
| xn |
| xn-1 |
| yn+1 |
| yn |
| yn |
| yn-1 |
(1)若x1,x3,x5成等比数列,求参数λ的值;
(2)当λ>0时,证明
| xn+1 |
| yn+1 |
| xn |
| yn |
| x1-y1 |
| x2-y2 |
| x2-y2 |
| x3-y3 |
| xn-yn |
| xn+1-yn+1 |
| λ |
| λ-1 |