1.
(2y + 1)² — 4y² = 5
(2y + 1)² — (2y)² = 5
(2y + 1 — 2y)(2y + 1 + 2y) = 5
4y + 1 = 5
4y = 5 — 1 = 4; y = 1;
2.
9x² — 1 — (3x — 2)² = 0
(3x)² — 1² — (3x — 2)² = 0
(3x — 1 — 3x + 2)(3x — 1 + 3x — 2) = 0
6x — 3 = 0
6x = 0,5;
3.
x + (5x + 2)² = 25 * (1 + x²)
x + 25x² + 20x + 4 = 25 + 25x²
20x + x = 25 — 4
21x = 21; x = 1.