Question

solve by suitable identities
(7x + 3)²?​

Answer 1

Answer:

(7x+3) ^2

(7x) ^2 + (3) ^2 + 2 × 7x × 3

49x^2 + 9 + 42x

Hope it helps you..

Answer 2

The expression is in the form of (a+b)² = a² + b² + 2ab

Here , a = 7x and b = 3

[Substituting the values ]

$\implies \tt{ {(7x + 3}^{2} = {(7x)}^{2} + {(3)}^{2} + 2(7x)(3)} \\ \implies \tt{ {49x}^{2} + 9 + 42x}$

Hence , Solved !!

Something you need to keep in mind :

• Having presence of mind while solving.
• These type of questions are very and are usually for 2 to 3 marks .
• Always keep in mind the way we derive the identity rather than mugging it up !!

Here is the derivation of the identity used :

$\implies \tt{ {(a + b)}^{2} = (a + b)(a + b)} \\ \implies \tt{a(a + b) + b(a + b)} \\ \implies \tt{ {a}^{2} + ab + ab + {b}^{2} } \\ \implies \tt{ {a}^{2} + 2ab + {b}^{2} }$

Hence , derived and solved !!