2) a) x² -7 =a
a² - 4a - 45 = 0
D₁ = 4 + 45 = 49
a₁ = 2 + 7 =9
a₂ = 2-7 = -5
x² - 7 =9
x² = 16
x₁/₂ = +-4
x² - 7 =-5
x² = 2
x₁/₂ = +-√2
Ответ: 4; -4; √2; -√2
б) x² + 2x =a
a² - 2a - 3 =0
1-3 = -2
a₁ = -1 a₂ = 3
x² +2x =-1 x² + 2x - 3=0
x² + 2x +1=0 1+2-3 = 0
D₁ =2-2=0 x₁ = 1 x₂ = -3
x = -1
Ответ: -1; 1; -3
в) x² - x +1 = a
x² - x -7 =a-8
a(a-8) = 65
a² - 8a - 65 =0
D₁ = 16 +65 = 81
a₁ = 4+ 9= 13 a₂ = 4-9=-5
x² - x +1=13 x² - x +1 =-5
x² - x - 12=0 x² - x + 6 =0
D = 1+48=49 D = 1 - 24 < 0
x₁ = 4 корней нет
x₂ = -3
Ответ: 4; -3