Question

(3x-5) . (x-5) + x² = 0

Answer 1

(3x - 5).(x - 5) + x² = 0
3x.x + 3x.(-5) - 5x - 5.(-5) + x² = 0
3x² - 15x - 5x +25 + x² = 0
3x² - 20x + 25 + x² = 0
4x² - 20x + 25 = 0
a = 4; b = - 20; c = 25
Δ = b² - 4ac
Δ = (-20)² - 4.4.25
Δ = 400 - 16.25
Δ = 400 - 400
Δ = 0

x = - b +/- √Δ    =  - (-20) +/- √0
      --------------      --------------------
             2a                    2.4

x = 20  (:4)
      -----
        8   (:4)

x =   5
      ------
        2

Answer 2

3x²-15x-5x+25+x²=0
4x²-20x+25=0

∆=(-20)²-4.4.25
∆=400-400
∆=0

x= 20/2.4
x=20/8
x=5/2