计算 ①(a+b)²-(a-b) ②(a+b-c)² ③(x-y+z)(x+y+z)
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计算 ①(a+b)²-(a-b) ②(a+b-c)² ③(x-y+z)(x+y+z)
计算 ①(a+b)²-(a-b) ②(a+b-c)² ③(x-y+z)(x+y+z)
计算 ①(a+b)²-(a-b) ②(a+b-c)² ③(x-y+z)(x+y+z)
①(a+b)²-(a-b)²
=a²+2ab+b²-a²+2ab-b²
=4ab
②(a+b-c)²
=a²+b²+c²+2ab-2ac-2bc
③(x-y+z)(x+y+z)
=(x+z)²-y²
=x²+2xz+z²-y²
①
(a+b)²-(a-b)
=a²+2ab+b²-a+b
②
(a+b-c)²
=(a+b)²-2c(a+b)+c²
=a²+b²+2ab-2ac-2bc+c²
=a²+b²+c²+2ab-2ac-2bc
③
(x-y+z)(x+y+z)
=(x+z-y)(x+z+y)
=(x+z)²-y²
=x²+2xz+z²-y²
①(a+b)²-(a-b)
=a²+2ab+b²-a+b
②(a+b-c)²
=(a+b)²-2c(a+b)+c²
=a²+2ab+b²-2ab-2bc+c²
③(x-y+z)(x+y+z)
=(x+z)²-y²
=x²+2xz+z²-y²