完全平方公式题计算:(1)(-1
虽明知绝不可被采纳,但也忍不住动手一下:
①
(-1-2x)^2
=[-(1+2x)]^2
=(1+2x)^2
=1+4x+4x^2
②
[(-5+x)(-5-x)]^2
=[-(5+x)(-5+x)]^2
=(x^2-25)^2
=x^4-50x^2+625
③
(x+3)^2-(x+2)(x-1)
=(x^2+6x+9)-(x^2+x-2)
=5x+11
④
(3x-a)(3x+a)(9x^2-a^2)
=(9x^2-a^2)(9x^2-a^2)
=(9x^2-a^2)^2
=81x^4-18a^2x^2+a^4
⑤
(x+y)^2-(x-y)^2
=(x^2+2xy+y^2)-(x^...全部
虽明知绝不可被采纳,但也忍不住动手一下:
①
(-1-2x)^2
=[-(1+2x)]^2
=(1+2x)^2
=1+4x+4x^2
②
[(-5+x)(-5-x)]^2
=[-(5+x)(-5+x)]^2
=(x^2-25)^2
=x^4-50x^2+625
③
(x+3)^2-(x+2)(x-1)
=(x^2+6x+9)-(x^2+x-2)
=5x+11
④
(3x-a)(3x+a)(9x^2-a^2)
=(9x^2-a^2)(9x^2-a^2)
=(9x^2-a^2)^2
=81x^4-18a^2x^2+a^4
⑤
(x+y)^2-(x-y)^2
=(x^2+2xy+y^2)-(x^2-2xy+y^2)
=4xy
或者,
(x+y)^2-(x-y)^2
=[(x+y)+(x-y)][(x+y)-(x-y)]
=(2x)·(2y)
=4xy
⑥
(x-2y+4)(x+2y-4)
=[x-(2y-4)][x+(2y-4)]
=x^2-(2y-4)^2
=x^2-4(y-2)^2
=x^2-4(y^2-4y+4)
=x^2-4y^2+16y-16。
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