已知x=-2,x+y+z=-2.8,求x2(-y-z)-3.2x(z+y)的值.
问题描述:
已知x=-2,x+y+z=-2.8,求x2(-y-z)-3.2x(z+y)的值.
答
∵x=-2,x+y+z=-2.8
∴y+z=-0.8
原式=(z+y)(-x2-3.2x)
=(-0.8)(-4+6.4)
=-0.8×2.4
=-1.92