已知x=2,x+y+z=-2.8,求x^2(-y-z)-3.2x(z+y)的值

题目

已知x=2,x+y+z=-2.8,求x^2(-y-z)-3.2x(z+y)的值
用因式分解啊

答案

答：
x=2,x+y+z=-2.8
2+y+z=-2.8
y+z=-4.8
x²(-y-z)-3.2x(z+y)
=-x(y+z)(x+3.2)
=-2×(-4.8)×(2+3.2)
=9.6×5.4
=51.84