已知x1+x2=-5,x1x2=3,求下列各式的值(1)x1²x2+x1x2² (2) (x1+3)(x2+3)
问题描述:
已知x1+x2=-5,x1x2=3,求下列各式的值
(1)x1²x2+x1x2² (2) (x1+3)(x2+3)
答
(1)x1²x2+x1x2²
=x1x2(x1+x2)
=3×(-5)
=-15
(2)(x1+3)(x2+3)
=x1x2+3(x1+x2)+9
=3+3×(-5)+9
=-3