2.a)

Note you may leave the solution in exponential form when the exponent is large as in this problem.

b)

An interesting thing happens if we substitute these values back into the original equation to determine if the solutions are correct. The 
x = 5 works fine; however, when x = -2 is substituted in and you check it on you calculator you will find that will display an error. This occurs because if you recall that the logarithm function is the inverse of the exponential function and if you check its graph you will see that the argument is always positive - you cannot take the logarithm of a negative number. Therefore, the root x = -2 is called an extraneous root for this equation and the only root is x = 5 .