Question

Evaluate using suitableIdentities. 1. (2a + 7) (2a – 7)​

Answer 1

Answer:

(2a)^2- (7)^2

Step-by-step explanation:

The anwer is

(2a)^2- (7)^2

Answer 2

Answer:

Step-by-step explanation:

Identity :

$(a+b)(a-b)=a^{2}-b^{2}$

L.H.S =$(a+b)(a-b)$

R.H.S =$a^{2}-b^{2}$

Proof:  By applying distributive law in left-hand side,

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

On multiplying each term,

                        $(a+b)(a-b)=a^{2}-a b+a b-b^{2}$

                         $(a+b)(a-b)=a^{2}-b^{2}$

                          L.H.S. = R.H.S.                                                              

Given:

An expression , $E=(2a+7)(2a-7)$

To find:

Evaluate the given expression

Solution:

Step 1:

The given expression is of the form, $(a+b)(a-b)$

Step 2:

Formula :  $(a+b)(a-b)=a^{2} -b^{2}$

Here , $a=2a$  and $b=7$

Substitute in formula,

$=(2a)^{2} -7^{2} \\\\=4a^{2}-49$

#SPJ3