x - 4 = 5²x - 4 = 25x = 25 + 4x = 291 - 3x = 2²1 - 3x = 4- 3x = 4 - 1- 3x = 33x = - 3x = - 125 - x² = 4²- x² - 16 + 25 = 0- x² + 9 = 0x² - 9 = 0D = b² - 4ac = 0² - 4 × 1 × ( - 9) = 36 = 6²x₁ = 0 + 6/2 = 3x₂ = 0 - 6/2 = - 3x² - 256 = 12²x² - 256 - 144 = 0x² - 400 = 0D = b² - 4ac = 0² - 4 × 1 ( - 400) = 1600 = 40²x₁ = 0 + 40 / 2 = 20x₂ = 0 - 40 / 2 = - 20x + 7 = 7²x + 7 = 49x = 49 - 7x = 426x - 1 = 1²6x = 1 + 16x = 2x = 2/6x = 1/3x + 2 - 81 = 12²x - 79 = 144x = 144 + 79x = 223625 - x² = 15²- x² + 625 = 225- x² = 225 - 625- x² = - 400x² = 400x - 400 = 0D = b² - 4ac = 0² - 4 × 1 × ( - 400) = 1600 = 40²x₁ = 0 + 40 / 2 = 20x₂ = 0 - 40 / 2 = - 20