(x +- y)² = x² +- 2xy + y²
a² - b² = (a - b)(a + b)
28x + 49x² + 4 = 0
(7x + 2)² = 0
7x = -2
x = -2/7
---
0.01y² + 10000 - 20y = 0
(0,1y - 100)² = 0
0,1y = 100
y = 1000
---
(3x - 5)² - 16 = 0
(3x - 5)² - 4² = 0
(3x - 5 - 4)(3x - 5 + 4) = 0
3x = 9
x₁ = 3
3x = 1
x₂ = 1/3
