4计算道题,11:30 ,要正确的
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4计算道题,11:30 ,要正确的
运用乘法公式计算:
(1).(3x-5)²-(2x+7)²
(2).(x+y+1)(x+y-1)
(3).(2x-y-3)²
(4).[(x+2)(x-2)]² (
运用乘法公式计算:
(1).(3x-5)²-(2x+7)²
(2).(x+y+1)(x+y-1)
(3).(2x-y-3)²
(4).[(x+2)(x-2)]² (
(1).(3x-5)²-(2x+7)²=(3x-5+2x+7)(3x-5-2x-7)=(5x+2)(x-12)=5x²-58x-24
(2).(x+y+1)(x+y-1)=(x+y)²-1
(3).(2x-y-3)²=(2x-y)²-2(2x-y)*3+3²=4x²-4xy-12x+y²+6y+9
(4).[(x+2)(x-2)]² =(x²-4)²=x²*x²-8x²+16
(2).(x+y+1)(x+y-1)=(x+y)²-1
(3).(2x-y-3)²=(2x-y)²-2(2x-y)*3+3²=4x²-4xy-12x+y²+6y+9
(4).[(x+2)(x-2)]² =(x²-4)²=x²*x²-8x²+16