4 * (1/16) ^x+15 * (1/4) ^x-4=0

4 * (1/2) ^4x+15 * (1/2) ^2x-4=0

произвожу замену (1/2) ^2x=t

ln ((1/2) ^2x) = ln t

2x*ln (1/2) = ln t

x=ln t / (2ln (1/2))

4t^2+15t-4=0

D=15^2+4*4*4=289

t1=-4 (не подходит),

t2=0.25

x=ln0.25 / (2*ln0.5) = 1