Question

Use suitable identity to find (2a -7) (2a-7)
class 8th Maths​

Answer 1

★Answer :-

$\rm{ \bf 4a^2 -28a+49}\; is\;the\;answer$

★Step-By-Step-Explanation :-

$\rm (2a-7)(2a-7)$

$\rm= (2a-7)^2$

★Using Suitable Identity :-

$\boxed{\underline{\tt (x-y)^2=x^2-2xy+y^2}}$

Thus , we have

x = 2a , y = 7

$\rm\implies (2a-7)^2=(2a)^2-2[(2a)(7)]+(7)^2$

$\rm\implies (2a-7)^2=2^2a^2-4a[(7)]+(7)^2$

$\rm\implies (2a-7)^2=4a^2-28a+49$

★Additional Information :-

$\rm\bigstar\underline{\bf Identity\; 1}$

$\rm (a+b)^2=(a+b)(a+b)$

$\rm =a(a+b)+b(a+b)$

$\rm =a^2+ab+ab+b^2$

$\rm =a^2+2ab+b^2$

$\rm\bigstar\underline{\bf Identity\; 2}$

$\rm (a-b)^2=(a-b)(a-b)$

$\rm =a(a-b)-b(a-b)$

$\rm= a^2-ab-ab+b^2$

$\rm =a^2-2ab+b^2$

$\rm\bigstar\underline{\bf Identity\; 3}$

$\rm (a+b)(a-b)=a(a-b)+b(a-b)$

$\rm =a^2-ab+ab-b^2$

$\rm =a^2-b^2$

$\rm\bigstar\underline{\bf Identity\; 4}$

$\rm (x+a)(x+b)=x(x+b)+a(x+b)$

$\rm =x^2+bx+ax+ab$

$\rm = x^2+x(a+b)+ab$

▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬