If x − y = 7 and xy = 9,


If x − y = 7 and xy = 9, find the value of x2 + y2


We have:

$(x-y)^{2}=x^{2}-2 x y+y^{2}$

$\Rightarrow x^{2}+y^{2}=(x-y)^{2}+2 x y$

$\Rightarrow x^{2}+y^{2}=7^{2}+2 \times 9 \quad(\because x-y=7$ and $x y=9)$

$\Rightarrow x^{2}+y^{2}=7^{2}+2 \times 9$

$\Rightarrow x^{2}+y^{2}=49+18$

$\Rightarrow x^{2}+y^{2}=67$



Leave a comment


Click here to get exam-ready with eSaral

For making your preparation journey smoother of JEE, NEET and Class 8 to 10, grab our app now.

Download Now