初中數學問題

2007-10-23 12:32 am

1a. Expand (x+y)²
1b. Using the result of (a), find the result (4a+5)²

回答 (3)

2007-10-23 12:37 am

✔ 最佳答案

1a.(x+y)2
= x2+ 2xy+y2
By (a+b)2= a2+ 2ab+b2

1b.(4a+5)²
= (4a)2+ 2(4a)(5)+(5)2
=16a2+ 40a +25

👍 0 👎 0

2007-10-23 12:46 am

1a
(x+y)²
=(x+y) * (x+y)
=x*x+x*y+y*x+y*y
= x² +xy +xy +y²
=x²+2xy+y²

1b.
(4a+5)²
=(4a)² + 2(4a) * (5) + (5)²
=16a² + 30a+25

參考: 自己

👍 0 👎 0

2007-10-23 12:43 am

1a.(x+y)2
= x^2+ 2xy+y^2
By (a+b)2= a^2+ 2ab+b^2

1b.(4a+5)²
= (4a)^2+ 2(4a)(5)+(5)^2
=16a^2+ 40a +25

參考: myself

👍 0 👎 0