Question

if x =3,y= 1,find the value of 9x²+ 49y²+ xy using suitable identity

Answer 1

Answer :

We know x = 3 And y = 1
And
9x² + 49y² + xy

We wrie it , As :

$\Rightarrow$9x² + 49y² + xy + 41xy - 41xy

$\Rightarrow$( 3x )² + ( 7y )² + 42xy - 41xy

$\Rightarrow$( 3x )² + ( 7y )² + 2 ( 3x ) ( 7y ) - 41xy

$\Rightarrow$( 3x + 7y )² - 41xy

Now we substitute value of x and y , we get

$\Rightarrow$( 3 $\times$ 3 + 7 $\times$ 1 )² - 41 $\times$ 3 $\times$ 1

$\Rightarrow$( 9 + 7 )² - 123

$\Rightarrow$( 16 )² - 123

$\Rightarrow$256 - 123

$\Rightarrow$133 ( Ans )