If x - y = 25 and xy = 78, then what is the value of $x^2 + y^2 $ ?
Answer & explanation
Correct answer: option 2
If x - y = 25
xy = 78,
then what is the value of $x^2 + y^2 $
( a - b )2 = $a^2 + b^2 $- 2ab
( 25 )2 = $x^2 + y^2 $ - 2(78)
625 = $x^2 + y^2 $ - 156
$x^2 + y^2 $ = 781