9x+2x²-3(x+3分之2x²)其中x=-2 先化简,再求值

问题描述:

9x+2x²-3(x+3分之2x²)其中x=-2 先化简,再求值

9x+2x²-3(x+3分之2x²)
=9x+2x²-3x-2x²
=6x
=6x(-2)
=-12
不懂的欢迎追问.1、4m-7n-2(m-2n) 2、-(x²-2xy-y²)+(5x²-2xy-3y²) 化简4m-7n-2(m-2n)=4m-7n-2m+4n=2m-3n-(x²-2xy-y²)+(5x²-2xy-3y²)=-x²+2xy+y²+5x²-2xy-3y²=4x²-2y²