计算:(1)(4x-1)(x+4) (2)(-2x-1/2)(x-1) (3)(x-2)(x+3)-2x²
问题描述:
计算:(1)(4x-1)(x+4) (2)(-2x-1/2)(x-1) (3)(x-2)(x+3)-2x²
(4)(a+1)(a-1/2)
(5)(3x-2y)(3x+2y)
(6)(3x-2)²
(7)(2x-5y)(3x-5y+6)
答
(1)(4x-1)(x+4) =4x²+16x-x-4=4x²+15x-4
(2)(-2x-1/2)(x-1) =-2x²+2x-1/2x+1/2=-2x²+3/2x+1/2
(3)(x-2)(x+3)-2x²=x²+x-6-2x²=-x²+x-6
(4)(a+1)(a-1/2) =a²-1/2a+a-1/2=a²+1/2a-1/2
(5)(3x-2y)(3x+2y)=(3x)²-(2y)²=9x²-4y²
(6)(3x-2)²=(3x)²-2×3x×2+2²=9x²-12x+4
(7)(2x-5y)(3x-5y+6)=6x²-10xy+12x-15xy+25y²-30y=6x²-25xy+25y²+12x-30y