答:
| |x+3|-|x-3| |>3
两边平方:
(x+3)^2-2|(x+3)(x-3)|+(x-3)^2>9
2x^2+18-2|x^2-9|>9
2x^2+9>2|x^2-9|
两边平方:
4x^4+36x^2+81>4(x^4-18x^2+81)
36x^2+81>-72x^2+324
36x^2+72x^2>324-81
108x^2>243
x^2>243/108=81/36=9/4
x>3/2或者x
答:
| |x+3|-|x-3| |>3
两边平方:
(x+3)^2-2|(x+3)(x-3)|+(x-3)^2>9
2x^2+18-2|x^2-9|>9
2x^2+9>2|x^2-9|
两边平方:
4x^4+36x^2+81>4(x^4-18x^2+81)
36x^2+81>-72x^2+324
36x^2+72x^2>324-81
108x^2>243
x^2>243/108=81/36=9/4
x>3/2或者x