Solve the simultaneous equations.

a. xy = 64

log_x y = 2

b. 2^x = 4^y

2lg y = lg x + lg 5

c. log₄(x + y) = 2 log₄ x

log₄ y = log₄ 3 + log₄ x

d. xy = 640

2 log₁₀ x – log₁₀ y = 2

e. log₁₀ a = 2 log₁₀ b

log₁₀ (2a – b) = 1

f. 4^xy = 2^x+5

log₂ y – log₂ x = 1