Question

resolva as seguintes equaçoes do 2 grau incompletas:a)9x² -5=0 b)7x² +2=30 c)2x² -90=8 d)8x² =60-7x²

Answer 1

Explicação passo-a-passo:

a)

$\sf 9x^2-5=0$

$\sf 9x^2=5$

$\sf x^2=\dfrac{5}{9}$

$\sf x=\pm\sqrt{\dfrac{5}{9}}$

• $\sf x'=\dfrac{\sqrt{5}}{3}$

• $\sf x"=\dfrac{-\sqrt{5}}{3}$

$\sf S=\left\{\dfrac{-\sqrt{5}}{3},\dfrac{\sqrt{5}}{3}\right\}$

b)

$\sf 7x^2+2=30$

$\sf 7x^2=30-2$

$\sf 7x^2=28$

$\sf x^2=\dfrac{28}{7}$

$\sf x^2=4$

$\sf x=\pm\sqrt{4}$

• $\sf x'=2$

• $\sf x"=-2$

$\sf S=\{-2,2\}$

c)

$\sf 2x^2-90=8$

$\sf 2x^2=8+90$

$\sf 2x^2=98$

$\sf x^2=\dfrac{98}{2}$

$\sf x^2=49$

$\sf x=\pm\sqrt{49}$

• $\sf x'=7$

• $\sf x"=-7$

$\sf S=\{-7,7\}$

d)

$\sf 8x^2=60-7x^2$

$\sf 8x^2+7x^2=60$

$\sf 15x^2=60$

$\sf x^2=\dfrac{60}{15}$

$\sf x^2=4$

$\sf x=\pm\sqrt{4}$

• $\sf x'=2$

• $\sf x"=-2$

$\sf S=\{-2,2\}$