(4x-7)(6x+5)-(3x+2)(8x-9)<5
(24x^2-22x-35)-(24x^2-11x-18)<5
-11x-17<5
-11x<22
x>-2还是看不懂,是用到什么公式了吗?就是普通的多项式的乘法(x+a)(x+b)=x^2+(a+b)x+ab(4x-7)(6x+5)-(3x+2)(8x-9)=(24x^2-42x+20x-35)-(24x^2+16x-27x-18)=(24x^2-22x-35)-(24x^2-11x-18) =-11x-17 所以(4x-7)(6x+5)-(3x+2)(8x-9)<5 -11x<22x>-2