(x-2)(x-3)+2(x+6)(x-5)-3(x²-7x+13),再求其值,其中x=3½.

问题描述:

(x-2)(x-3)+2(x+6)(x-5)-3(x²-7x+13),再求其值,其中x=3½.

先将上式整理一下
=x²-5x+6+2(x²+x-30)-3x²+21x-39
=x²-5x+6+2x²+2x-60-3x²+21x-39
=18x-93
再将x=3½代入上式
得出值=18√3-93

先展开,再整理得(x-2)(x-3)+2(x+6)(x-5)-3(x²-7x+13)
=x²-5x+6+(2x+12) (x-5)-3x²+21x-39= -2x²+16x-33+2x²+2x-60=18x-93
把x=3½ 代入上式,得
原式=18×3½.-93
=63-93 = -30

(x-2)(x-3)+2(x+6)(x-5)-3(x²-7x+13)
=(x²-5x+6)+2(x²+x-30)-3(x²-7x+13)
=x²-5x+6+2x²+2x-60-3x²+21x-39
=18x-93
=18*(3½)-93
=18*(7/2)-93
=63-93
=-30

(x-2)(x-3)+2(x+6)(x-5)-3(x²-7x+13)
=x²-5x+6+(2x+12) (x-5)-3x²+21x-39
= -2x²+16x-33+2x²+2x-60
=18x-93
把x=3½ 代入上式,得
原式=18×3½.-93
=63-93
= -30