# CAT Practice : Exponents and Logarithms

Carving a quadratic equations from an Exponents question is very useful.

Q.3: If 22x+4 – 17 × 2x+1 = –4, then which of the following is true?
1. x is a positive value
2. x is a negative value
3. x can be either a positive value or a negative value
4. None of these

Choice C. x can be either a positive value or a negative value

Click to watch video solution
Click to view the explanation as a slide show

## Detailed Solution

2x+4 – 17 × 2x+1 = – 4
2x+1 = y
22x+2 = y2
22(22x+2) – 17 × 2x+1 = –4
4y2 – 17y + 4 = 0
4y2 – 16y – y + y = 0
4y (y – 4) – 1 (y – 4) = 0
y = ${1 \over 4}$ or 4
2x+1 = ${1 \over 4}$ or 4
x + 1 = 2 or – 2
x = 1 or – 3

Correct Answer: x can be either a positive value or a negative value

## Our Online Course, Now on Google Playstore!

### Fully Functional Course on Mobile

All features of the online course, including the classes, discussion board, quizes and more, on a mobile platform.

### Cache Content for Offline Viewing

Download videos onto your mobile so you can learn on the fly, even when the network gets choppy!

## More questions from Exponents and Logarithms

With every extra hour you log in for this topic, it becomes exponentially simpler.