Question

Multiply the following using appropriate identities
3. (x-7)(x-7)
4 (3x - 1) (3x-8)​

Answer 1

$\Large\color{red}{\textbf{\textsf{answer:}}}$

$\bf{~~~~~~1.~~(x-7)(x-7)}$

$\bf{Identity~to~be~used:}$

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

$\tt{ : \longrightarrow (x)^{2}-2(x)(7)+(7)^{2}}$

$\tt{ : \longrightarrow {\color{red}{{\bf{x^{2}-14x+49}}}}}$

―――――――――――――――――――――――

$\bf{~~~~~~2.~~(3x-1)(3x-8)}$

$\bf{Identity~to~be~used:}$

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

$\tt{ : \longrightarrow (3x)^{2}+[(-1)+(-8)~]3x+(-1×-8)}$

$\tt{ : \longrightarrow 9x^{2}+(-9)3x+8}$

$\tt{ : \longrightarrow {\color{red}{{\bf{9x^{2}-27x+8}}}}}$