Question

× au quadrado menos ×menos 20 igual a 0

Answer 1

Oi....

$x^2-x-20=0\\\\Coeficientes:\;a=1,\;b=-1\;e\;c=-20\\\\\Delta=b^2-4ac\\\Delta=-1^2-4\cdot1\cdot(-20)\\\Delta=1+80\\\Delta=81\\\\x=\dfrac{-b\pm\sqrt{\Delta}}{2a}\\\\x=\dfrac{1\pm\sqrt{81}}{2\cdot1}\\\\x=\dfrac{1\pm9}{2}\\\\x_1=\dfrac{1+9}{2}=\dfrac{10}{2}=5\\\\x_2=\dfrac{1-9}{2}=\dfrac{-8}{2}=-4$

Espero ter ajudado.