Question

quais são as raizes da equução > X²-9X+20=0 ?

Answer 1

x e 3 
x.x = x²
3.3 = 9

Answer 2

Resolução da questão, veja:

$x^{2}-9x+20 = 0\\\\\\\ x= -b~+_{-}~\dfrac{ \sqrt{b^{2}-4~.~a~.~c}}{2~.~a}}\\\\\\x = 9~+_{-}~\dfrac{ \sqrt{(-9)^{2}-4~.~1~.~20}}{2~.~1}}\\\\\\ x = 9~+_{-}\dfrac{ \sqrt{81-80}}{2}}\\\\\\ x= 9~ +_{-}~\dfrac{ \sqrt{1}}{2}}\\\\\\ \Delta = 1 =\ \textgreater \ x' = x''\\\\\ x'=x'' = \dfrac{9 + 1}{2} = \ \textgreater \ x'=x'' = \dfrac{10}{2} =\ \textgreater \ \lare\boxed{\boxed{x'=x'' = 5.}}$

Espero que te ajude :).