Hej!
a)
x² - (2 - x)² = 8
x² - (4 - 4x + x²) = 8
x² - 4 + 4x - x² = 8
4x - 4 = 8 / + 4
4x = 12 / : 4
x = 3
b)
(3x + 1)² - 9x² = 7
9x² + 6x + 1 - 9x² = 7
6x + 1 = 7 / - 1
6x = 6 / : 6
x = 1
c)
(x + 1)² - (x + 1)(x - 1) = 12
x² + 2x + 1 - (x² - 1) = 12
x² + 2x + 1 - x² + 1 = 12
2x + 2 = 12 / - 2
2x = 10 / : 2
x = 5
Pozdrawiam! - Julka
