Question

prove LHS =RHS...using Identity

Answer 1

$\bf\huge\color{red}\mathfrak{ hello\: mate!}$

$\bf\color{red}\mathfrak{thanks \:for\: asking\: this\: question !}$

$<b> here's your answer!$

$\huge\color{blue}{ firstly, }$

LHS = (3x+7)² - 84x
= (3x)² + (7)² + 2(3x)(7) - 84x (since, (a+b)²= a²+b²+2ab)
= 9x² + 49 + 42x - 84x
= 9x² + 49 - 42x
= 9x² - 42x + 49

$\huge\color{blue}{ now, }$

RHS = (3x-7)²
= (3x)² + (7)² - 2(3x)(7) (since, (a-b)²= a²+b²-2ab)
= 9x² + 49 - 42x
= 9x² - 42x + 49

$\pink{\boxed{\bold{\underline{THUS,\: PROVED,\: L.H.S.\: = \:R.H.S.}}}}$

$\green{\boxed{\bold{\underline{ hope \: it \: is \: helpful}}}}$