Question

x方减6x减7小于等于零？

Answer 1

x^2-6x-7 ≤0
(x-7)(x+1)≤0
x-7≤0 且 x+1≥ 0 =》x≤7 且 x ≥ -1
x-7≥0 且 x+1≤ 0 =》 x ≥7 且 x≤-1 无解
故该不等式的解集为{x| -1≤x≤7}