If x > 0, What is the least possible value of -2√(5x) +

This topic has expert replies
Moderator
Posts: 7187
Joined: Thu Sep 07, 2017 4:43 pm
Followed by:23 members

Timer

00:00

Your Answer

A

B

C

D

E

Global Stats

If x > 0, What is the least possible value of -2√(5x) + x + 9 ?


A. 0
B. 1
C. √5
D. 4
E. 9

OA D

Source: e-GMAT

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 7223
Joined: Sat Apr 25, 2015 10:56 am
Location: Los Angeles, CA
Thanked: 43 times
Followed by:29 members

by Scott@TargetTestPrep » Tue May 21, 2019 6:26 pm
BTGmoderatorDC wrote:If x > 0, What is the least possible value of -2√(5x) + x + 9 ?


A. 0
B. 1
C. √5
D. 4
E. 9

OA D

Source: e-GMAT
Notice that (√x - √5)^2 = (√x)^2 + (√5)^2 - 2(√x)(√5) = x + 5 - 2√(5x). Therefore,

-2√(5x) + x + 9 = (√x - √5)^2 + 4

Since the minimum value of (√x - √5)^2 is 0, then the minimum value of -2√(5x) + x + 9 is:

(√x - √5)^2 + 4 = 0 + 4 = 4

Answer: D

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