把抛物线y=-3(x-1)^向上平移k个单位,所得抛物线与x轴交于点A(x1,0)和B(x2,0)如果(x1)^+(x2)^=26/9那么k=

问题描述:

把抛物线y=-3(x-1)^向上平移k个单位,所得抛物线与x轴交于点A(x1,0)和B(x2,0)如果(x1)^+(x2)^=26/9那么k=

y=-3(x-1)^2+k
3x^2-6x+3-k=0
x1+x2=2 x1x2=(3-k)/3
x1^2+x2^2=(x1+x2)^2-4x1x2=4-4(3-k)/3=26/9
k=25/6