1) x≠-1
34x² - 23x = x² - 4
33x² - 23x + 4 = 0
D = 529 - 528 = 1
x₁ = (23 - 1)/66 = 22/66 = 1/3
x₂ = (23 + 1)/66 = 24/66 = 4/11
2) x≠2
2x² - 21 = 5x - 2x²
4x² - 5x - 21 = 0
D = 25 + 336 = 361
x₁ = (5-19)/8 = -14/8 = -1,75
x₂ = (5+19)/8 = 24/8 = 3
3) x≠-3
4 - 8x = 34x² + x
34x² + 9x - 4 = 0
D = 81 + 544 = 625
x₁ = (-9-25)/68 = -34/68 = -0.5
x₂ = (-9+25)/68 = 16/68 = 4/17
4) x≠5
18 - 6x² = x² - 15x
7x² - 15x - 18 = 0
D = 225 + 504 = 729
x₁ = (15-27)/14 = -12/14 = -6/7
x₂ = (15+27)/14 = 42/14 = 3