中二數學(~急~)

(a+b)^2
=a^2+2ab+b^2

所以

(-7p+9p)²
=(-7p)^2+2(-7p)(9p)+(9p)^2
= 49p^2-126p^2+81p^2
=4p^2

beside,
(a+b)(a-b)
=a^2-b^2

(-7p+9p)²
=49p²+81p²
=130p²
希望幫到你
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=(-7p)^2+2(-7p)(9p)+(9p)^2
=49p^2-126p^2+81p^2
=4p^2

或者=(9p-7p)^2
=(9p)^2-2(7p)(9p)+(7p)^2
=81p^2-126p^2+49p^2
=4p^2

(^2)=2次方
希望幫到你＾＾

.(-7p+9p)²
=49p^2+81p^2
=p^2(49+81)
=p^2(130)
=130p^2

130p²

2007-09-19 18:42:46 補充：
(-7)²p² (9)²p²=130p²我想是差唔多= =