Question

Me ajuuuudeeeeeem!
Resolva as equações do 2 grau:
a) x² - 5x=0
b)x² -9=0
c)7x² - 4x=0
d)3x² - 27x=0
e)x² -90=0
f)16y² -81=0

Answer 1

$a) x^2-5x=0\\\\ x(x-5)=0\\ \\ x=0 \\\\ x-5=0\to x=5\\\\\\ S=(0;5)$




$b) x^{2} -9=0\\\\ x^{2} =9\to \\\\ x=\pm \sqrt{9} \to \\\\ x=\pm3\\\\\\ S=(-3;3)$




$c)7 x^{2} -4x=0\\\\ x(7x-4)=0\\\\ x=0\\\\ 7x-4=0\to 7x=4\to x= \frac{4}{7} \\\\\\ S=(0;\frac{4}{7} )$




$d)3 x^{2} -27x=0\\\\ x(3x-27)=0\\\\ x=0\to \\\\ 3x-27=0\to 3x=27\to x= \frac{27}{3} \to x=9\\\\\\ S=(0;9)$




$e) x^{2} -90=0\to x^{2} =90\to x=\pm \sqrt{90} \to \\\\ x=\pm \sqrt{2*5^2*5} \to \\\\ x=\pm 5\sqrt{2*5} \to \\\\ x=\pm 5 \sqrt{10} \\\\ \\ S=(-5 \sqrt{10};5 \sqrt{10})$




$f) 16y^2-81=0\\\\ 16y^2=81\to \\\\ y^2= \frac{81}{16} \to \\\\ y=\pm \sqrt{\frac{81}{16} } \to \\\\ y= \pm \frac{9}{4} \\\\\\ S=(-\frac{9}{4} ;\frac{9}{4} )$



Espero que tenha ajudado...