解不等式 x/(x^2-8x+15)》2
问题描述：
解不等式 x/(x^2-8x+15)》2
答
x/(x²-8x+15)-2≥0
(x-2x²+16x-30)/(x^2-8x+15)≥0
(2x²-17x+30)/(x²-8x+15)≤0
即(2x²-17x+30)(x²-8x+15)≤0
(2x-5)(x-6)(x-3)(x-5)≤0
零点是5/2,3,5,6
所以由穿针法
5/2≤x≤3,5≤x≤6
分母不等于0
所以5/2≤x