Question

x elevado a quarta potencia - 9 x ao quadrado +20 =0

Answer 1

Essa é uma Equação Biquadrada

$x^{4} -9 x^{2} +20=0\to x^{2} =y\\\\\\ y^{2} -9y+20=0\\ a=1;b=-9;c=20\\\\\\ \Delta=b^2-4ac\to \Delta=(-9)^2-4*1*20\to \Delta=81-80\to \Delta=1\\\\\\ y= \frac{-b+- \sqrt{\Delta} }{2a} \to y= \frac{-(-9)+- \sqrt{1} }{2*1} \to y= \frac{9+-1 }{2} \to \\\\\\ y'= \frac{9+1 }{2} \to y'= \frac{10 }{2} \to y'=5\\\\\\ y''= \frac{9-1 }{2} \to y''= \frac{8}{2} \to y''=4\\\\\\ S=(4;5)$