Question

Resolva as equações:
a) x2 - 4x = 0
b) x2 - 6x = 0
c) 2x2 + 8x = 0
d) 5x2 - 15x = 0​

Answer 1

a)

${x}^{2} - 4x = 0 \\ x.(x - 4) = 0 \\ x = 0 \\ \\ x - 4 = 0 \\ x = 0 + 4 \\ x = 4 \\ \\ x' = 0 \: | \: x'' = 4$

b)

${x}^{2} - 6x = 0 \\ x.(x - 6) = 0 \\ x = 0 \\ \\ x - 6 = 0 \\ x = 0 + 6 \\ x = 6 \\ \\ x' = 0 \: | \: x'' = 6$

c)

${2x}^{2} + 8x = 0 \\ 2x.(x + 4) = 0 \\ x.(x + 4) = 0 \\ x = 0 \\ \\ x + 4 = 0 \\ x = 0 - 4 \\ x = - 4\\ \\ x' = - 4 \: | \: x'' = 0$

d)

${5x}^{2} - 15x = 0 \\ 5x.(x - 3) = 0 \\ x.(x - 3) = 0 \\ x = 0 \\ \\ x - 3 = 0 \\ x = 0 + 3 \\ x = 3\\ \\ x' = 0 \: | \: x'' = 3$