Question

22) Resolva as equações por fatoração.
a) x2 - 81 = 0
b) x2 - 25 = 0
c) x2 - 64 = 0​

Answer 1

a)

$x^2-81=0\\\\x^2-81+81=0+81\\\\x^2=81\\\\x=\sqrt{81},\:x=-\sqrt{81}\\\\\sqrt{81}\\\\=9$

$-\sqrt{81}\\\\=-9$

$x=9,\:x=-9$

b)

$x\cdot \:2-25=0$

$x\cdot \:2-25+25=0+25\\\\\frac{x\cdot \:2}{2}=\frac{25}{2}\\\\x=\frac{25}{2}$

c)

$x\cdot \:2-64=0\\\\x\cdot \:2-64+64=0+64\\\\x\cdot \:2=64\\\\\frac{x\cdot \:2}{2}=\frac{64}{2}\\\\x=32$