Question

求解答这道数学题

Answer 1

x1+x2=-2(a-1)
x1*x2=aa-7a-4
x1*x2-3x1-3x2-2=0
x1*x2-3(x1+x2)-2=0
aa-7a-4 +6(a-1)-2=0
aa-7a-4+6a-6-2=0
aa-a-12=0
(a-4)(a+3)-0
a1=4. a2=-3
当a=4时

(1+4/(aa-4))*(a+2)/4=(1+1/3)*3/2=4/3*3/2=2
当a=-3时
(1+4/(aa-4))*(a+2)/4=(1+4/5)*(-1/3)=9/5*(-1/3)=-3/5

Answer 2

X1+X2=2(a-1) X1*X2=a^2-7a-4
a^2-7a-4+3*2(a-1)-2=0
a^2-a-12=0
a=4或a=-3
原式=a^2/(a^2-4) *(a+2)/a
=a/(a-2)=1+2/(a-2)
把a=4带入得原式=2
把a=-3带入得原式=3/5