Question

Qaunto É ?
A-) (7a+1) x (7a-1)=
b-) (2+9x)²=
c-) (6x-y)² =

Answer 1

a)
(7a + 1).(7a - 1)
= 7a.7a - 1.7a + 1.7a + 1.(-1) 
= 49a² - 7a + 7a - 1
= 49a² - 1

b)
(2 + 9x)²
= (2 + 9x) . ( 2 + 9x)
= 2.2 + 2.9x + 2.9x + 9x.9x
= 4 + 18x + 18x + 81x²
= 81x² + 36x + 4

c) 
= (6x - y)²  
= (6x - y).(6x - y) =  36x² - 2.6x.y + y²
= 6x.6x - y.6x - y.6x - y.(-y)
= 36x² - 6xy - 6xy + y²

= 36x² - 12xy + y²
 

Answer 2

a) (7a + 1) . (7a - 1) = 7a² - 1²
b) (2 + 9x)² =
2² + 2 . (2 . 9x) + 9x² = 4 + 36x + 81x²
c) (6x - y)² =
6x² - 2. (6x . y) + y² = 36x² -12xy + y²