Prove that the following equations are identities.
1) (x+2)^2-(x-2)^2=8x
LHS=?
RHS=?
LHS=RHS
maths f.2 easy
2007-10-09 4:35 am
回答 (4)
2007-10-09 5:27 pm
✔ 最佳答案
LHS = (x+2)^2-(x-2)^2= (x+2)(x+2)-(x-2)(x-2)
= [(x)(x+2)+2(x+2)]-[(x)(x-2)-2(x-2)]
= (x^2+2x+2x+4)-(x^2-2x-2x+4)
= (x^2+4x+4)-(x^2-4x+4)
= x^2+4x+4-x^2+4x-4
= 8x
= RHS
2008-02-04 8:02 pm
=(x+2+x-2)(x+2-x+2)
=(2x)(4)
=8x
這樣快好多﹗
=(2x)(4)
=8x
這樣快好多﹗
2007-10-09 4:48 am
直接expand幾易計,
不過有另一個計算方法,就係用a^2-b^2=(a+b)(a-b)呢條式
LHS=(x+2+x-2)(x+2-x+2)
=2x*4
=8x
=RHS
不過有另一個計算方法,就係用a^2-b^2=(a+b)(a-b)呢條式
LHS=(x+2+x-2)(x+2-x+2)
=2x*4
=8x
=RHS
2007-10-09 4:39 am
LHS = x^2 + 4x + 4 - x^2 + 4x - 4
= 8x
SO LHS= RHS
= 8x
SO LHS= RHS
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