Question

Resolva as equações.
A) x elevado a 2 menos 25 igual a 0
B) x elevado a 2 menos 25x igual a 0
C) x elevado a 2 menos 3x mais 2 igual a 0

Answer 1

Olá...

A)
$x^{2} -25=0 \\ x^{2} =25 \\ x=\pm \sqrt{25 } \\ x=\pm5 \\ \\ S=\{-5,+5\}$ 

B)
$x^{2} -25x=0 \\ x(x-25)=0 \\ x-25=0~~~~e~~~x=0 \\ x=25 \\ \\ S=\{0,25\}$ 

C)
$x^{2} -3x+2=0 \\ \\ a=1 \\ b=-3 \\ c=2 \\ \\ \Delta=b^2-4ac \\ \Delta=(-3)^2-4(1)(2) \\ \Delta=9-8 \\ \Delta=1 \\ \\ x= \frac{-b\pm \sqrt{\Delta} }{2a} =~~ \frac{-(-3)\pm \sqrt{1} }{2} =~~ \frac{3\pm1}{2} \\ \\ x'= \frac{3+1}{2} = \frac{4}{2} =2 \\ \\ x"= \frac{3-1}{2} = \frac{2}{2} =1 \\ \\ S=\{1,2\}$