2^x = 7, then 2^2x =?
a)49
b)7
c)128
d)64
e)32
Please assist with above problem.
2^x = 7, then 2^2x =? a)49 b)7 c)128 d)64 e)32
This topic has expert replies
-
- Master | Next Rank: 500 Posts
- Posts: 187
- Joined: Tue Sep 13, 2016 12:46 am
- MartyMurray
- Legendary Member
- Posts: 2131
- Joined: Mon Feb 03, 2014 9:26 am
- Location: https://martymurraycoaching.com/
- Thanked: 955 times
- Followed by:140 members
- GMAT Score:800
Exponents of the same base can be added when powers of that base are multiplied.
So 2²ˣ = 2ˣ * 2ˣ.
So if 2²ˣ = 7, then 2²ˣ = 7 x 7 = 49.
Alternatively, you can express 2²ˣ in this way, (2ˣ)², because to get from the second expression to the first you would multiply the exponent inside the parentheses by the exponent outside the parentheses.
If 2ˣ = 7, then 2²ˣ = (2ˣ)² = 49.
The correct answer is A.
So 2²ˣ = 2ˣ * 2ˣ.
So if 2²ˣ = 7, then 2²ˣ = 7 x 7 = 49.
Alternatively, you can express 2²ˣ in this way, (2ˣ)², because to get from the second expression to the first you would multiply the exponent inside the parentheses by the exponent outside the parentheses.
If 2ˣ = 7, then 2²ˣ = (2ˣ)² = 49.
The correct answer is A.
Marty Murray
Perfect Scoring Tutor With Over a Decade of Experience
MartyMurrayCoaching.com
Contact me at [email protected] for a free consultation.
Perfect Scoring Tutor With Over a Decade of Experience
MartyMurrayCoaching.com
Contact me at [email protected] for a free consultation.
-
- GMAT Instructor
- Posts: 2630
- Joined: Wed Sep 12, 2012 3:32 pm
- Location: East Bay all the way
- Thanked: 625 times
- Followed by:119 members
- GMAT Score:780
Another approach:
(aᵇ)ᶜ = (aᶜ)ᵇ
so
(2²)ˣ = (2ˣ)²
and we're told that (2ˣ)² = 49, so that's our answer!
(aᵇ)ᶜ = (aᶜ)ᵇ
so
(2²)ˣ = (2ˣ)²
and we're told that (2ˣ)² = 49, so that's our answer!