Question

先化简,再求值:4(-x+1)^2-2(-x+1)(-1-x)+3(1-x^2)其中x=-1/2.

Answer 1

原式=4(x²-2x+1)-2[(-x)²-1²]+3(1-x²)
=4x²-8x+4-2x²+2+3-3x²
=-x²-8x+9
=-1/4+4+9
=51/4

Answer 2

4(-x+1)^2-2(-x+1)(-1-x)-3(1-x^2)
=4(x-1)²-2(x-1)(x+1)+3(x-1)(x-1)
=4(x-1)²+(x-1)(x+1)
=4x²-8x+4+x²-1
=5x²-8x+3 将x=-1/2代入
解得=5/4+7
=8（1/4）＝33/4
祝学业有成！~~

Answer 3

4(-x+1)^2-2(-x+1)(-1-x)+3(1-x^2)
=4(1-x)²+2(1-x)(1+x)+3(1-x)(1+x)
=4(1-x)(1-x)+5(1-x)(1+x)
=(1-x)(4-4x+5+5x)
=(1-x)(9+x)
将x=-1/2代入

=(1+1/2)(9-1/2)
=51/4

Answer 4

4(-x+1)^2-2(-x+1)(-1-x)-3(1-x^2)
=4(x-1)²-2(x-1)(x+1)+3(x-1)(x-1)
=4(x-1)²+(x-1)(x+1)
=4x²-8x+4+x²-1
=5x²-8x+3
当x=-1/2时
原式=5/4+4+3
=33/4

Answer 5

-（x-1）(x+9)=12.75