Question

25x=20x-4
4+x(x-4)=x
preciso de ajuda

Answer 1

25x = 20x - 4
25x - 20x = - 4
5x = - 4
x = - 4/5


4 + x . (x - 4) = x
4 + x^2 - 4x = x
x^2 - 4x + 4 - x = 0
x^2 - 5x + 4 = 0

a = 1
b = - 5
c = 4

Delta = b^2 - 4.a.c
Delta = (- 5)^2 - 4.1.4
Delta = 25 - 16
Delta = 9

x = - b +- VDelta / 2.a
x = - (- 5) +- V9 / 2.1
x = 5 +- 3 / 2

x' = 5 - 3 / 2
x' = 2/2
x' = 1

x" = 5 + 3 / 2
x" = 8/2
x" = 4

S = {1 , 4}