Let C and K be constants.If x^2+Kx+5 factors into (x+1)(x+C), then : Problem Solving (PS)

My Profile Logout

Test's Subscription Expires:

My Follow Feed Kudos My Error Log

Messages and Replies

Settings Mark All Read

See All

Applicant Notifications

Settings Mark All Read

See All

Global notifications

Settings Mark All Read

See All

Let C and K be constants.If x^2+Kx+5 factors into (x+1)(x+C), then

Sort by Date

Sort by Kudos

Author

Message

TAGS:

Hide Tags

Current Student

Joined: 12 Aug 2015

Posts: 2638

Schools: Boston U '20 (M)

GRE 1: Q169 V154

Let C and K be constants.If x^2+Kx+5 factors into (x+1)(x+C), then [#permalink]

Show Tags

22 Apr 2017, 13:02

00:00

Difficulty:

15% (low)

Question Stats:

78% (00:55) correct

22% (00:58) wrong

based on 104 sessions

HideShow timer Statistics

Let \(C\) and \(K\) be constants.If \(x^2+Kx+5\) factors into \((x+1)*(x+C)\), then what is the value of \(K\)?

A)0
B)5
C)6
D)8
E)Cannot be determined

Source => NOVA.

Spoiler: OA

_________________

Give me a hell yeah ...!!!!!

MBA Dating:- B-SCHOOL with the MOST ATTRACTIVE Women

MBA Recruiting:- EMPLOYMENT AND SALARY STATISTICS AT TOP B-SCHOOLS IN THE US! (2018)

MBA Financing:- INDIAN PUBLIC BANKS vs PRODIGY FINANCE!

Getting into HOLLYWOOD with an MBA!

The MOST AFFORDABLE MBA programs!

STONECOLD's BRUTAL Mock Tests for GMAT-Quant(700+)

AVERAGE GRE Scores At The Top Business Schools!

Manager

Joined: 05 Nov 2016

Posts: 89

Re: Let C and K be constants.If x^2+Kx+5 factors into (x+1)(x+C), then [#permalink]

Show Tags

22 Apr 2017, 16:35

Matching constants value on the given equation with its factor ... we get C=5 and K=c+1=6
Option C

Posted from my mobile device
_________________

Kudos are always welcome ... as well your suggestions

Intern

Joined: 06 May 2015

Posts: 23

Re: Let C and K be constants.If x^2+Kx+5 factors into (x+1)(x+C), then [#permalink]

Show Tags

26 Jun 2017, 05:21

we have been given that X^2+kx+5 in to factor equtations (x+1) (x+c)
now solve this (x+1) (x+c) = x^2+x+cx+c
x^2 +x(1+c) + c
Now we know that equation is x^2 +kx+5 form so compare this equation with x^2 +X(1+c) + C
we will comclude that c=5, kx will be = x(1+c) i.e. 6x since c=5
so the value of k=6

Manager

Joined: 03 Feb 2017

Posts: 75

Location: Australia

GMAT 1: 720 Q48 V40

Re: Let C and K be constants.If x^2+Kx+5 factors into (x+1)(x+C), then [#permalink]

Show Tags

26 Jun 2017, 05:36

For the quadratic equation \(x^2\)+Kx+5; sum of roots = K and product of roots = 5

Roots given as (x+1) and (x+C)
Hence, product of the roots = 1*C = 5
Hence C=5

Sum of the roots = K = 1+5 = 6
Answer C

Senior SC Moderator

Joined: 22 May 2016

Posts: 2034

Let C and K be constants.If x^2+Kx+5 factors into (x+1)(x+C), then [#permalink]

Show Tags

27 Jun 2017, 07:32

stonecold wrote:

Let \(C\) and \(K\) be constants.If \(x^2+Kx+5\) factors into \((x+1)*(x+C)\), then what is the value of \(K\)?

A)0
B)5
C)6
D)8
E)Cannot be determined

Source => NOVA.

Because we are given one factor's integer, (x+1), I would just factor \(x^2+Kx+5\).

With (x+1) and (x + ___), thinking about FOIL where last two terms multiplied must equal 5, we need:

1*__ = 5. 1*5 = 5. Write the factors and multiply.

(x+1)(x+5) = \(x^2 + 6x + 5\).

K = 6, Answer C.
_________________

The only thing more dangerous than ignorance is arrogance.
-- Albert Einstein

Retired Moderator

Joined: 19 Mar 2014

Posts: 948

Location: India

Concentration: Finance, Entrepreneurship

Schools: HBS '20, Stanford '20, Wharton '20, Kellogg '20, CBS '20, Haas '20

GPA: 3.5

Re: Let C and K be constants.If x^2+Kx+5 factors into (x+1)(x+C), then [#permalink]

Show Tags

27 Jun 2017, 13:24

Let \(C\) and \(K\) be constants.If \(x^2+Kx+5\) factors into \((x+1)*(x+C)\), then what is the value of \(K\)?

\(x^2+Kx+5\) = \((x+1)*(x+C)\)

As we know that \(a^2 + 2ab + b^2\) = \((a+b) * (a+b)\)

After comparing the above equation with our equation we can see that

b = c = 5

We can also directly equate \(2ab = kx = 6x\)- However in order to make it more clear we will understand in detail per below steps.

\(x^2+Kx+5\) = \(x^2 + 5x + 1x + 5\)

\(x^2+Kx+5\) = \(x^2 + 6x + 5\)

\(kx = 6x\)

\(k = 6\)

Hence, the answer is C
_________________

"Nothing in this world can take the place of persistence. Talent will not: nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not: the world is full of educated derelicts. Persistence and determination alone are omnipotent."

Best AWA Template: https://gmatclub.com/forum/how-to-get-6-0-awa-my-guide-64327.html#p470475

Non-Human User

Joined: 09 Sep 2013

Posts: 8454

Re: Let C and K be constants.If x^2+Kx+5 factors into (x+1)(x+C), then [#permalink]

Show Tags

01 Oct 2018, 07:16

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________