计算:①(a+1) 2 -2(a-1) 2 ②(3-x 2 )(-x 2 -3).③(x+1) 2 -5(x+1)(x-1)+3(x-1) 2 ④
计算:①(a+1)2-2(a-1)2②(3-x2)(-x2-3).③(x+1)2-5(x+1)(x-1)+3(x-1)2④(2x-1)2(2x+1)2⑤(x+2y-z)(...
计算:①(a+1) 2 -2(a-1) 2 ②(3-x 2 )(-x 2 -3).③(x+1) 2 -5(x+1)(x-1)+3(x-1) 2 ④(2x-1) 2 (2x+1) 2 ⑤(x+2y-z)(x-2y-z)
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①(a+1) 2 -2(a-1) 2 =a 2 +2a+1-2(a 2 -2a+1) =a 2 +2a+1-2a 2 +4a-2 =-a 2 +6a-1; ②(3-x 2 )(-x 2 -3) =-(3-x 2 )(x 2 +3) =-(9-x 4 ) =x 4 -9; ③(x+1) 2 -5(x+1)(x-1)+3(x-1) 2 =x 2 +2x+1-5(x 2 -1)+3(x 2 -2x+1) =x 2 +2x+1-5x 2 +5+3x 2 -6x+3 =-10x 2 -4x+9; ④(2x-1) 2 (2x+1) 2 =(4x 2 -1) 2 =16x 4 -8x 2 +1; ⑤(x+2y-z)(x-2y-z) =[(x-z)+2y][(x-z)-2y] =(x-z) 2 -4y 2 =x 2 -2xz+z 2 -4y 2 . |
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