y=x²+2(a-2)x+2a-4设函数图象与x轴交点的横坐标为x1 与 x2|x1/x2|为2/3,若a<2,求a的值.其实前半段我会的:∵a<2,x1x2=2a-4∴x1x2=2a-4<0所以x1/x2<0,x1/x2= - 2/3我会了:x1=-2/3x2 1/3x2=-2a+4x2=6a-6,-2/3x2
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![y=x²+2(a-2)x+2a-4设函数图象与x轴交点的横坐标为x1 与 x2|x1/x2|为2/3,若a<2,求a的值.其实前半段我会的:∵a<2,x1x2=2a-4∴x1x2=2a-4<0所以x1/x2<0,x1/x2= - 2/3我会了:x1=-2/3x2 1/3x2=-2a+4x2=6a-6,-2/3x2](/uploads/image/z/10251285-69-5.jpg?t=y%3Dx%26sup2%3B%2B2%EF%BC%88a-2%EF%BC%89x%2B2a-4%E8%AE%BE%E5%87%BD%E6%95%B0%E5%9B%BE%E8%B1%A1%E4%B8%8Ex%E8%BD%B4%E4%BA%A4%E7%82%B9%E7%9A%84%E6%A8%AA%E5%9D%90%E6%A0%87%E4%B8%BAx1+%E4%B8%8E+x2%7Cx1%2Fx2%7C%E4%B8%BA2%2F3%2C%E8%8B%A5a%EF%BC%9C2%2C%E6%B1%82a%E7%9A%84%E5%80%BC.%E5%85%B6%E5%AE%9E%E5%89%8D%E5%8D%8A%E6%AE%B5%E6%88%91%E4%BC%9A%E7%9A%84%EF%BC%9A%E2%88%B5a%EF%BC%9C2%EF%BC%8Cx1x2%3D2a-4%E2%88%B4x1x2%3D2a-4%EF%BC%9C0%E6%89%80%E4%BB%A5x1%2Fx2%EF%BC%9C0%2Cx1%2Fx2%3D+-+2%2F3%E6%88%91%E4%BC%9A%E4%BA%86%EF%BC%9Ax1%3D-2%2F3x2+1%2F3x2%3D-2a%2B4x2%3D6a-6%2C-2%2F3x2)
y=x²+2(a-2)x+2a-4设函数图象与x轴交点的横坐标为x1 与 x2|x1/x2|为2/3,若a<2,求a的值.其实前半段我会的:∵a<2,x1x2=2a-4∴x1x2=2a-4<0所以x1/x2<0,x1/x2= - 2/3我会了:x1=-2/3x2 1/3x2=-2a+4x2=6a-6,-2/3x2
y=x²+2(a-2)x+2a-4
设函数图象与x轴交点的横坐标为x1 与 x2
|x1/x2|为2/3,若a<2,求a的值.
其实前半段我会的:
∵a<2,x1x2=2a-4
∴x1x2=2a-4<0
所以x1/x2<0,x1/x2= - 2/3
我会了:
x1=-2/3x2
1/3x2=-2a+4
x2=6a-6,
-2/3x2²=2a-4
x2²=6a-3
(6a-6)²=6a-3
a1=4/5,a2=2/3 希望大家再接再厉,认真答题,给真正需要帮助的给予有益的帮助!Thank you all the same!
y=x²+2(a-2)x+2a-4设函数图象与x轴交点的横坐标为x1 与 x2|x1/x2|为2/3,若a<2,求a的值.其实前半段我会的:∵a<2,x1x2=2a-4∴x1x2=2a-4<0所以x1/x2<0,x1/x2= - 2/3我会了:x1=-2/3x2 1/3x2=-2a+4x2=6a-6,-2/3x2
x1+x2=-2a+4=t>0;
x1*x2=2a-4=-t;
x1/x2= - 2/3
x2=3t,x1=-2t;
-6t^=-t
t=1/6
a=23/12
由韦达定理得
X1+X2=4-2a x1x2=2a-4 又因为x1/x2=2/3 x1=-3/5 x2=-2/5 ∴a=49/12
x1与x2同号。
∵X1X2=-b/a=-[2(a-2)]又∵a<2
∴x1x2大于零∴x1x2同号。
上面的补充答案就要出来啦
x1/x2=-2/3;
就是2a-4=-2/3;
a=5/3;
∵[X1/X2]的绝对值=2/3,X1X2=2(a-2)<0
(a<2) ∴ X1与 X2异号,∴X1/X2=-2/3
X1=-2/3 X2 ∵X1+ X2=-2(a-2), X1X2=2(a-2)
∴1/3 X2=2/3X22, ∴X1=-1/3,X2=2/3
∴2(a-2)=-1/6, a=23/12
(a=49/12应该不对,超过a的范围了)
X1+X2=4-2a x1x2=2a-4 x1/x2=2/3 x1=-3/5 x2=-2/5 ∴a=49/12
后半段:
不妨设:x1=-2b,x2=3b(b不为0)
所以,x1+x2=b,x1x2=-6bb;
又因为,x1+x2=-2(a-2)=-x1x2
所以,b=6bb
所以,b=1/6
所以,x1+x2=-2(a-2)=b=1/6
解得:a=23/12