2*9^ (x^2-4x+1) + 42*6^ (x^2-4x) - 15*4^ (x^2-4x+1) = 0 [-1; 3 ]

18*9^ (x²-4x) + 42*3^ (x²-4x) * 2^ (x²-4x) - 60*4^ (x²-4x) = 0/4^ (x²-4x)

18 * (9/4) ^ (x²-4x) + 42 * (3/2) ^ (x²-4x) - 60=0

(3/2) ^ (x²-4x) = a

18a²+42a-60=0

3a²+7a-10=0

D=49+120=169

a1 = (-7-13) / 6=-10/3⇒ (3/2) ^ (x²-4x) = - 10/3 нет решения

a2 = (-7+13) / 6=1⇒ (3/2) ^ (x²-4x) = 1

x²-4x=0

x (x-4) = 0

x=0∈[-1; 3] U x=4∉[-1; 3]

Ответ х=0