Помогите решить

5^ (x+1) + 3*5^-x=16

(5^x) * 5 + 3 * (1/5^x) - 16 = 0 / * 5^x

5 * (5^2x) - 16 * (5^x) + 3 = 0

5^x = t

5 * (t^2) - 16t + 3 = 0

D = 256 - 4*5*3 = 196

t1 = (16 - 14) / 10

t1 = 1/5

t2 = (16 + 14) / 10

t2 = 3

5^x = 1/5

5^x = 5^ (- 1)

x1 = - 1

5^x = 3

x2 = log (5) 3