当X=4,(x-2)(x-3)+(x-4)(x-5)-2(x+5)(x-6)求它的值.解答及过程

题目

当X=4,(x-2)(x-3)+(x-4)(x-5)-2(x+5)(x-6)求它的值.解答及过程

答案

(x-2)(x-3)+(x-4)(x-5)-2(x+5)(x-6)
=(x²-5x+6)+(x²-9x+20)-2(x²-x-30)
=x²-5x+6+x²-9x+20-2x²+2x+60
=-12x+86
=-12×4+86
=-48+86
=38