Question

(3a+7)²-84a = (3a-7)² by using idinties
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Answer 1

$\huge\mathbb{SOLUTION:-}$

$\bf\underline{\underline{Step\:By\:step\: Explanation:-}}$

• Identity used

$\boxed{\sf{ (a+b){}^{2}=a{}^{2}+b{}^{2}+2ab}}$

$\boxed{\sf{ (a-b){}^{2}=a{}^{2}+b{}^{2}-2ab}}$

• Now:-
• L.H.S

$\sf\implies (3a+7){}^{2}-84a\\ \\ \sf\implies (3a){}^{2}+(7){}^{2}+2\times 3a\times 7-84a\\ \\ \sf\implies 9a{}^{2}+49+ 42a-84a\\ \\ \sf\implies 9a{}^{2}+49-42a\:\:\\ \\ \tt\:\:\:or\:\:(3a-7){}^{2}$

• Now R.H.S

$\sf\implies (3a-7){}^{2}\\ \\ \sf\implies (3a){}^{2}+(7){}^{2}-2\times 3a\times 7\\ \\ \sf\implies 9a{}^{2}+49-42a\\ \\ \tt\:\:\:or\:\:(3a-7){}^{2}$

$\sf\leadsto \:\:\: L.H.S=R.H.S\\ \\ \tt\implies (3a+7){}^{2}-84a=(3a-7){}^{2}\:\:\:{\red{\sf{Hence\: proved ! ! !}}}$

Answer 2

Step-by-step explanation:

Refer to this attachment.❤

$\huge\underline\mathcal\red{♡Thanks♡}$