Solve this math problem without calculating anything

2 + 2 + (2)^2 + (2)^3 + (2)^4 + (2)^5 + (2)^6 + (2)^7 + (2)^8 = ?

Answer is (2)^9

it was a question on the GMAT practice test. How do I save time by solving this without calculating every single numbers (since you can't use a calculator).

I'm sure there's a trick maybe?

The trick to doing it is factoring:
2 + 2 + 2^2 + 2^3 + 2^4 + 2^5 + 2^6 + 2^7 + 2^8 =
2^2 + 2^2 + 2^3 + 2^4 + 2^5 + 2^6 2^7 + 2^8

Each step keep factoring out a 2^2, using the exponent rule to add the exponents:

2^2( 1 + 1 + 2 + 2^2 + 2^3 + 2^4 + 2^5 + 2^6) =
2^2( 2^2 + 2^2 + 2^3 + 2^4 + 2^5 + 2^6)

2^4( 1 + 1 + 2 + 2^2 + 2^3 + 2^4)=
2^4( 2^2 + 2^2 + 2^3 + 2^4)

2^6( 1 + 1 + 1 + 2^2)=
2^6( 2^2 + 2^2)

2^8(1 +1)
2^8(2)= (2)^9

This problem involves knowing the exponential rule (a^x)(a^y)=(a^x+y). Also I recommend you memorize powers of 2