Question

去括号练习题

去括号练习题
化简:
-(x-6y)-(-7+3y)
3(2a^2-b^2)-2(3b^2-2a^2)
(m^2-2mn+n^2)-(m^2+2mn+n^2)
-1/2(x+y)-1/4(x-y)
-3/4(x^2-x)+2(x^2-x)
还有化简求值,2（x－3x^2＋1）－3（2x^2－x－2）其中x＝2

Answer 1

-(x-6y)-(-7+3y)
=-x+6y+7-3y
=-x+3y+7

3(2a²-b²)-2(3b²-2a²)
=6a²-3b²-6b²+4a²
=10a²-9b²

(m²-2mn+n²)-(m²+2mn+n²)
=m²-2mn+n²-m²-2mn-n²
=-4mn

-1/2(x+y)-1/4(x-y)
=-x/2-y/2-x/4+y/4
=-3x/4-y/4

-3/4(x²-x)+2(x²-x)
=(-3/4+2)(x²-x)
=5/4(x²-x)
=5x²/4-5x²/4

2(x-3x²+1)-3(2x²-x-2)
=2x-6x²+2-6x²+3x+6
=-12x²+x+8
=-12×2²+2²+8
=-36