Question

Resolva as equações do 2º grau,sendo U=R.
a)7x²+2=30
b)2x²-90=8
c)4x²-27=x²
d)8x²=60-7x²

Answer 1

a)7x²+2=30
7x²=30-2
7x²=28
x²=28/7
x²=4
x=√4
x=2
 
b)2x²-90=8
2x²=8+90
2x²=98
x²=98/2
x²=49
x=√49
x=7


c)4x²-27=x²
4x²-x²=+27
3x²=27
x²=27/3
x²=9
x=√9
x=3


d)8x²=60-7x²
8x²+7x²=60
15x²=60
x²=60/15
x²=4
x=√4
x=2

Espero ajudar

Answer 2

$a)7 x^{2} +2=30\\\\ 7 x^{2} =30-2\to \\\\7 x^{2} =28\to \\\\ x^{2} = \frac{28}{7} \to\\\\ x^{2} =4\to \\\\ x=\pm 4\to \\\\ x=\pm2\\\\\\ S=(-2;2)$



$b)2 x^{2} -90=8\\\\ 2 x^{2} =8+90\to \\\\ 2 x^{2} =98\to \\\\ x^{2} = \frac{98}{2} \to \\\\ x^{2} =49\to \\\\ x=\pm \sqrt{49} \to\\\\ x=\pm7\\\\\\S=(-7;7)$



$c)4 x^{2} -27= x^{2} \\\\ 4x^{2} - x^{2} =27\to \\\\ 3 x^{2} =27\to \\\\ x^{2} = \frac{27}{3} \to \\\\ x^{2} =9\to\\\\ x=\pm \sqrt{9} \to\\\\ x=\pm3\\\\\\ S=(-3;3)$



$d)8 x^{2} =60-7 x^{2} \\\\ 8 x^{2} +7 x^{2} =60\to\\\\ 15 x^{2} =60\to\\\\ x^{2} = \frac{60}{15} \to\\\\ x^{2} =4\to \\\\ x=\pm \sqrt{4} \to\\\\ x=\pm2\\\\\\ S=(-2;2)$



Espero ter ajudado...