jika x1 dan x2 adalah...

x²+5x-10
x1 + x2 = -b/a = -5/1 = -5
x1x2 = c/a = -10/1 = -10
x1²+x2² = (x1+x2)²-2x1x2 = (-5)²-2(-10) = 25-(-20) = 25+20 = 45 ..