BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

If x^2 – 4x = 5, then one possible value of x – 4 =

Expert replies
Source: — Problem Solving |

BTGModeratorVI wrote:
Sun Aug 02, 2020 6:59 am
If x^2 – 4x = 5, then one possible value of x – 4 =

A. -9
B. -5
C. -3
D. -1
E. 5

Answer: B
Source: Manhattan prep
x^2 – 4x = 5
Rearrange to get: x^2 – 4x - 5 = 0
Factor: (x - 5)(x + 1) = 0
So, either x = 5 or x = -1

If x = 5, then x - 4 = 5 - 4 = 1 [not among the answer choices]
If x = -1, then x - 4 = (-1) - 4 = -5. Great!

Answer: B

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Join the discussion

BTGModeratorVI wrote:
Sun Aug 02, 2020 6:59 am
If x^2 – 4x = 5, then one possible value of x – 4 =

A. -9
B. -5
C. -3
D. -1
E. 5

Answer: B
Solution:

We will set the equation equal to 0, factor the quadratic, and find the zeros:

x^2 - 4x - 5 =0

(x - 5)(x + 1) = 0

x = 5 OR x = -1

We see that x - 4 could equal 1 or -5.

Answer: B

Scott Woodbury-Stewart
Founder and CEO
[email protected]

Image

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

ImageImage
Join the discussion