If x+y=9 and xy=10, what is the value of x^3+y^3?
from first equation 9-x = y sub into 2nd equation
x(9-x) =10
-x^2+9x-10 = 0 quadratic formula shows x = 9/2 +- sqrt41 /2 if x = 1.29844 or 7.70156
y = 7.70156 or 1.29844
then x^3 + y^3 = 459
Thanks!!
\(x^3 + y^3 = (x + y)(x^2 - xy + y^2) = (\color{blue}x + y\color{black})((\color{blue}x + y\color{black})^2\, - \,3\color{red}xy\color{black})\)
Now you can substitute the values.
+37155 
