A F. 2 Maths question - Expansion by using identities
Expand 2(3p-7q)(-7q-3p).
Please show your working steps clearly and explain your answer in details.
A F. 2 Maths question - Expansion by using identities
2007-01-10 7:09 am
回答 (4)
2007-01-10 7:13 am
✔ 最佳答案
2(3p-7q)(-7q-3p)=-2(3p-7q)(7q+3p)
=-2(3p-7q)(3p+7q)
=-2[(3p)^2-(7q)^2]
=-2(9p^2-49q^2)
=-18p^2+98q^2
2007-01-09 23:21:05 補充：
補充：a²-b² = (a-b)(a b) (a-b)² = a²-2ab b²(a b)² = a² 2ab b²a³-b³ = (a-b)(a² ab b²)a³ b³ = (a b)(a²-ab b²)
2007-01-11 1:36 am
2(3p-7q)(-7q-3p)
=2(-7q+3p)(-7q-3p)
=2[(-7q)^2-(3p)^2]
=2(49q^2-9p^2)
=98q^2-18p^2
#
P.S.: I am in F.2 too.
2007-01-10 17:38:26 補充：
because of (a+b)(a-b) =a^2-b^2
=2(-7q+3p)(-7q-3p)
=2[(-7q)^2-(3p)^2]
=2(49q^2-9p^2)
=98q^2-18p^2
#
P.S.: I am in F.2 too.
2007-01-10 17:38:26 補充：
because of (a+b)(a-b) =a^2-b^2
2007-01-10 3:12 pm
= 2(3p-7q)(-7q-3p)
＊將(-7q-3p)抽個負數出黎>>&;gt;>-1(3p+7q)
= -2(3p-7q)(3p+7q)
= -2[3p(3p+7q) -7q (3p+7q)]
= -2[9p^2 +21pq - 21pg - 49q^2]
= -2[9p^2 - 49q^2]
= 98q^2 - 18p^2
＊將(-7q-3p)抽個負數出黎>>&;gt;>-1(3p+7q)
= -2(3p-7q)(3p+7q)
= -2[3p(3p+7q) -7q (3p+7q)]
= -2[9p^2 +21pq - 21pg - 49q^2]
= -2[9p^2 - 49q^2]
= 98q^2 - 18p^2
2007-01-10 8:24 am
= 2(3p-7q)(-7q-3p)
＊將(-7q-3p)抽個負數出黎>>>>-1(3p+7q)
= -2(3p-7q)(3p+7q)
= -2[3p(3p+7q) -7q (3p+7q)]
= -2[9p^2 +21pq - 21pg - 49q^2]
= -2[9p^2 - 49q^2]
= 98q^2 - 18p^2
＊將(-7q-3p)抽個負數出黎>>>>-1(3p+7q)
= -2(3p-7q)(3p+7q)
= -2[3p(3p+7q) -7q (3p+7q)]
= -2[9p^2 +21pq - 21pg - 49q^2]
= -2[9p^2 - 49q^2]
= 98q^2 - 18p^2
參考: 自己計
收錄日期: 2021-04-25 16:52:04
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070109000051KK04757