Question

If 3^x=81 then (3^x+3)(4^x+1) must be equal to.....?

Answer 1

${3}^{x} = 81 \\ {3}^{x} = {3}^{4} \\ x = 4 \\ ( {3}^{x} + 3)( {4}^{x} + 1) \\ = ( {3}^{4} + 3)( {4}^{4} + 1) \\ = (81 + 3)(256 + 1) \\ = (84)(257) \\ = 21588$