Question

(7-x)^4-4(x-7)^2-21=0
решите пожалуйста​

Answer 1

(7-x)^4-4(x-7)^2-21=0

(x-7)^2 = (7-x)^2

(x-7)^4-4(x-7)^2-21=0

замена (x-7)^2 = y ≥ 0

y^2 - 4y - 21 = 0

D = 16 + 84 = 100

y12 = (4 +- 10)/2 = -7   3

y = -7 < 0 нет

y = 3

(x - 7)^2 = 3

x - 7 = ± √3

x₁₂ = 7 ± √3