Question

x+y=5 and xy=15, find x^2+y^2

Answer 1

Use:

\[\large x^2 + y^2 = (x+y)^2 - 2xy\]

Answer 2

Solve this:

\[\large x^2 + y^2 = (5)^2 - 2(15)\]

Can you do it now??

Answer 3

yes.... thank you

Answer 4

Wait how the result can be negative??

I am in doubt now..

Wait..

Answer 5

k

Answer 6

\(x_1=\frac12(5-i\sqrt{35})\)
\(x_2=\frac12(5+i\sqrt{35})\)
\(x_1,x_2\) are complex numbers, so it is okay.