Question

先化简,再求值

1/2a-2(a-1/2b的平方)-(3/2a-1/3b的平方),其中a=-2,b=2/3
2x的平方-{-3x+5+[4x的平方-（3x的平方-x-1)]-3｝-5,其中x=-11/2

Answer 1

1/2a-2(a-1/2b²)-(3/2a-1/3b²)
=1/2a-2a+b²-3/2a+1/3b²
=(1/2a-2a-3/2a)+(b²+1/3b²)
=-3a+4/3b²
=-3×(-2)+4/3×(2/3)²
=6+4/3×4/9
=6+16/27
=178/27

2x²-{-3x+5+[4x²-(3x²-x-1)]-3}-5
=2x²-[-3x+5+(4x²-3x²+x+1)-3]-5
=2x²-(-3x+5+4x²-3x²+x+1-3)-5
=2x²+3x-5-4x²+3x²-x-1+3-5
=(2x²-4x²+3x²)+(3x-x)+(-5-1+3-5)
=x²+2x-8
=(-11/2)²+2×(-11/2)-8
=121/4-11-8
=45/4

追问

谢谢谢谢,你绝对是好人~