Question

Khai triển HDT:

1. ( 2x + y² ) 

2. ( 7 + 3x - y) ( 7 - 3x + y )

3. ( 6/5 - 5x )² 

Answer 1

` @Answer`

`2,(7+3x-y)(7-3x+y)`

`=(7+3x)^2 - y^2`

`3, (6/5 - 5x)^2`

`=(6/5)^2 - 2 . 6/5 . 5x+ (5x)^2`

`= 36/25 - 12x + 25x^2`

Công thức :

`(x-y)(x+y) = x^2 - y^2`

`(x+y)^2=x^2+2xy+y^2`

`+,` Đề `1:(2x+y^2)` ngoài ngoặc có gì ạ ?

 

Answer 2

2)

(7 + 3x - y)(7 - 3x + y)

= [7 + (3x - y)][7 - (3x + y)]

= 7² - (3x - y)²

= 49 - (3x - y)²

= 49 - (9x² - 6xy + y²)

= 49 - 9x² + 6xy - y²