Question

Resolva as seguintes equações do 2ºgrau incompletas:
a)7x²+2=30 b)x²-81=0 c)21=7x² d)8x²=60-7x²

Answer 1

a)
$7 {x}^{2} + 2 = 30$
$7 {x}^{2} = 30 - 2 = 28 \\ {x = 28 \div 7}^{2} \\ x = 4$
b)x^2-81=0
x=81-0
x=81

c)21=7x^2
x^2=21÷7
x=3

d)8x^2=60-7x^2
8x^2+7x^2=60
15x^2=60
x^2=60÷15
x=4