1) x² + 6x - 16= 0
D = 6² - 4*(-16) = 36 + 64 = 100
X₁ = (- 6 + √100)/2 = (- 6 + 10)/2 = 2
X₂ = (- 6 - √100)/2 = (- 6 - 10)/2 = - 8
2a) x² - 7x + 12= 0
D = 7² - 4*12= 49 - 48 = 1
X₁ = (7 + 1)/2 = 4
X₂ = (7 - 1)/2 = 3
x² - 7x + 12 = (x - 3)(x - 4)
б) 5x² - 5x - 10 = 0
x² - x - 2 = 0
X₁ = 2
X₂ = - 1 - по теореме, обратной теореме Виетта
5x² - 5x - 10 = 5(x - 2)(x + 1)
3) x² - 16x + 100 = ( x² - 16x + 64) + 36 = (x - 8)² + 36