Answer
$874x²+66x+25376$
Work Step by Step
$f(x)=$ Electricity generated (in gigawatts) from geothermal sources
$g(x)=$ Electricity generated (in gigawatts) from wind power
$f(x)=-20x²+156x+14437$
$g(x)=894x²-90x+10939$
$f(x)+g(x)=874x²+66x+25376$