先化简(x-2)(x-3)+2(x+6)(x-5)-3(x²-7x+13),再求其值,其中x=3又2/1

问题描述:

先化简(x-2)(x-3)+2(x+6)(x-5)-3(x²-7x+13),再求其值,其中x=3又2/1

化简得=18x-93
=-20

(x-2)(x-3)+2(x+6)(x-5)-3(x²-7x+13)
=x^2-5x+6+2x^2+2x-30-3x^2+21x-39
=18x-63
=18*7/2-63
=63-63
=0

=(x^2-5x+6)+2(x^2+x-30)-3(x^2-7x+13)
=18x-93
自己求值吧。
没有“3又2/1”这个数的!

(x-2)(x-3)+2(x+6)(x-5)-3(x²-7x+13)
=x²-5x+6+2x²+2x-60-3x²+21x-39
=18x-93
=63-93
=-30

(x-2)(x-3)+2(x+6)(x-5)-3(x²-7x+13)
=x²-5x+6+2(x²+x-30)-3x²+21x-39
=3x²-3x-54-3x²+21x-39
=18x-93
x=3又2/1
18x=63
所以原来的式子=63-93=-30