Find the following squares by using the identities:
$( i)$. $( b-7)^{2}$
$( ii)$. $( xy+3z)^{2}$
$( iii)$. $( 6x^{2}-5 y)^{2}$
$( iv)$. $(\frac{2}{3}m+\frac{3}{2}n)^{2}$
$( v)$. $( 0.4p-0.5q)^{2}$
$( vi)$. $( 2xy+5y)^{2}$


Solution:

$( i)$. $( b-7)^2$

$=b^2+7^2-2( b)( 7)$

$=b^2+49-14b$                 $\because [(a-b)^2=a^2+b^2-2ab]$


$( ii)$. $( xy+3z)^2$

$=( xy)^2+( 3z)^2+2( xy)( 3z)$

$=x^2y^2+9z^2+6xyz$                 $\because [(a+b)^2=a^2+b^2+2ab]$


$( iii)$. $( 6x-5y)^2$

$=( 6x)^2+( 5y)^2-2( 6x)( 5y)$

$=36x^2+25y^2-60xy$                 $\because [( a-b)^2=a^2+b^2-2ab]$


$( iv)$. $( \frac{2}{3}m+\frac{3}{2}n)^2$

$=( \frac{2}{3}m)^2+( \frac{3}{2}n)^2+2( \frac{2}{3}m)( \frac{3}{2}n)$

$=\frac{4}{9}m^2+\frac{9}{4}n^2+2mn$                 $\because [(a+b)^2=a^2+b^2+2ab]$


$( v)$. $(0.4p-0.5q)^2$

$=( 0.4p)^2+( 0.5q)^2-2( 0.4p)( 0.5q)$

$=0.16p^2+0.25q^2-4pq$              $\because [( a-b)^2=a^2+b^2-2ab]$

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Updated on: 10-Oct-2022

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