Question

Quanto é x ao quadrado + 7 = 7 x - 3 ?

Answer 1

$x^2+7=7x-3\\x^2-7x+7+3=0\\x^2-7x+10=0\\\\x=\frac{-b\pm \:\sqrt{b^2-4ac}}{2a}\\x=\frac{7\pm \:\sqrt{7^2-\left(4\cdot 1\cdot 10\right)}}{2\cdot 1}\\x=\frac{7\pm \:\sqrt{49-40}}{2}\\x=\frac{7\pm \:\sqrt{9}}{2}\\x=\frac{7\pm \:3}{2}\\\\\boxed{\bold{x_1=\frac{7+\:3}{2}=\frac{10}{2}=5}}\\\boxed{\bold{x_2=\frac{7-\:3}{2}=\frac{4}{2}=2}}$