（x-3）(x+2)-9/4
(2x-1)(2x-5)>=4x(x-5)
4x^2-12x+5>=4x^2-20x
8x>=-5
x>=-8/5综上,x>=-8/5
3^2m-3n+1
=3^2m×3^（-3n）×3
=﹙3^m﹚²×1/﹙3^n﹚³×3
=5²×1/2³×3
=75/8
（x-3）(x+2)-9/4
(2x-1)(2x-5)>=4x(x-5)
4x^2-12x+5>=4x^2-20x
8x>=-5
x>=-8/5综上,x>=-8/5
3^2m-3n+1
=3^2m×3^（-3n）×3
=﹙3^m﹚²×1/﹙3^n﹚³×3
=5²×1/2³×3
=75/8