3x-2(5+2x)
=3x-10-4x
=-10-x
(x-3 x 的平方+1)-2(x的平方-1+3x)
=x-3x²+1-2x²+2-6x
=-5x²-5x+3
5(2x-7y)-3(4x-10y)
=10x-35y-12x+30y
=-2x-5y
3x-2(5+2x)
=3x-10-4x
=-10-x
(x-3 x 的平方+1)-2(x的平方-1+3x)
=x-3x²+1-2x²+2-6x
=-5x²-5x+3
5(2x-7y)-3(4x-10y)
=10x-35y-12x+30y
=-2x-5y