(2-x)(x-3)(x平方-5x-14)大于等于100(初一的题目)
问题描述:
(2-x)(x-3)(x平方-5x-14)大于等于100(初一的题目)
答
(2-x)(x-3)(x^2-5x-14)>=100
-(x-2)(x-3)(x^2-5x-14)>=100
(x-2)(x-3)(x^2-5x-14)(x^2-5x+6)(x^2-5x-14)+100(x^-5x)^2-8(x^2-5x)-84+100(x^-5x)^2-8(x^2-5x)+16(x^2-5x-4)^2(x^2-5x-4)^2>=0
所以
x^2-5x-4=0
x^2-5x+25/4-25/4-4=0
(x-5/2)^2-41/4=0
(x-5/2-√41/2)(x-5/2+√41/2)=0
x=5/2+√41/2或x=5/2-√41/2
答
(2-x)(x-3)(x^2-5x-14)≥ 100-(x-2)(x-3)(x^2-5x-14)≥ 100(x-2)(x-3)(x^2-5x-14)≤ -100(x^2-5x+6)(x^2-5x-14)≤ -100(x^2-5x)^2 - 8(x^2-5x) -84 ≤ -100(x^2-5x)^2 - 8(x^2-5x) +16 ≤ 0{(x^2-...