Question

determine o valor de X, real, para que o número complexo: a) x+(x²-7x+12) seja real

Answer 1

$x^{2} - 7x - x +12 => x^{2} - 8x +12$
Δ=$b^{2} - 4ac$
$a=1 | b=-8 | c=12$
Δ=$-8^{2} - 4.1.12$
Δ=$64 - 60$
Δ=$4$

$x=\frac{-b + - \sqrt{DELTA} }{2.a}$
$x= \frac{-(-8) +- \sqrt{4} }{2.1}$
$x_{1} = \frac{8+2}{2} = \frac{10}{2} = 5 \\ x_{2} = \frac{8-2}{2} = \frac{6}{2} = 3$