3x(2x-5)-(4x+1)(x-7)
(2x+3)(2x-3)-3(x-5)2
解説動画 ≫
3x(2x-5)-(4x+1)(x-7)
= 6x2-15x-(4x2-27x-7)
= 6x2-15x-4x2+27x+7
= 2x2+12x+7
(2x+3)(2x-3)-3(x-5)2
= 4x2-9-3(x2-10x+25)
= 4x2-9-3x2+30x-75
= x2+30x-84
【練習】
4x(3x+1)+(5x-2)(2x+3)
22x2+15x-65x(x-4)-(2x-1)(3x-4)
-x2-9x-4(3x-1)2+5(x+2)(x-3)
14x2-11x-298(x-3)(x+2)-(3x-4)(3x+4)
-x2-8x-32