I need to see how the answer is obtained. Thanks for helping.

Start by factoring out the square root. Then add up what's left and put that into "a power of three" form.Given that 3^(7/2)+3^(5/2)+3^(3/2)+42(3^1/2) may be expressed as 3^k find the value of k. (ans given states k=4.5)
I need to see how the answer is obtained. Thanks for helping.