= 64^(t^3)*64^(-t/2)
= 64^(t^3)*(64^(-1/2))^t . . . . change the sum of exponents to a product
= 64^(t^3)*(1/√64)^t . . . . . . negative exponent signifies inverse, 1/2 power is sqrt
= 64^(t^3)/8^t . . . . . . . . . . . simplify
= (4^3)^(t^3)/8^t . . . . . . . . . .replace 64 with 4^3
= 4^(3t^3)/8^t . . . . matches the first selection only