If find x. 1/(9!) + 1/(10!) = x/(11!).

 

Here n! is read as n factorial. It can be written as n(n-1)! or n(n-1)(n-1)!

Expand the following using suitable identity (i) (x+2y+4z)² (ii) (-2x+3y+2z)². [ncert]

(i) (x + 2y + 4z) * iii * (- 2x + 3y + 2z) ^ 2

We know that  (a + b + c)² = a²+ b²+ c²+ 2ab + 2bc + 2ca

(i) (x + 2y + 4z)² = (x)² + (2y)²+ (4z)²+ 2(x)(2y)+2(2y)(4z) + 2(4z)(x)

= x² + 4y²+ 16z² + 4xy + 16yz + 8zx  Ans.

(ⅱ) (- 2x + 3y + 2z)²=(-2x)²+(3y)²+(2z)² +2(-2x)

(3y)+2(3y)(2z) + 2(2z)(- 2x)

 = 4x²+9y²+4z²-12xy+12yz-8zx  Ans.