GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 08 Dec 2019, 13:42

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

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

Author Message
TAGS:

### Hide Tags

Current Student
Joined: 12 Aug 2015
Posts: 2549
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

Updated on: 06 Jul 2019, 05:25
1
5
00:00

Difficulty:

15% (low)

Question Stats:

79% (01:07) correct 21% (01:12) wrong based on 97 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 GMAT
Difficulty Level: 550

_________________

Originally posted by stonecold on 22 Apr 2017, 13:02.
Last edited by SajjadAhmad on 06 Jul 2019, 05:25, edited 1 time in total.
Manager
Joined: 05 Nov 2016
Posts: 82
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
Intern
Joined: 06 May 2015
Posts: 22
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: 72
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
1
1
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
Senior SC Moderator
Joined: 22 May 2016
Posts: 3730
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, 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) = $$x^2 + 6x + 5$$.

_________________
SC Butler has resumed! Get two SC questions to practice, whose links you can find by date, here.

Never doubt that a small group of thoughtful, committed citizens can change the world; indeed, it's the only thing that ever has -- Margaret Mead
Retired Moderator
Joined: 19 Mar 2014
Posts: 917
Location: India
Concentration: Finance, Entrepreneurship
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.

$$x^2+Kx+5$$ = $$x^2 + 5x + 1x + 5$$

$$x^2+Kx+5$$ = $$x^2 + 6x + 5$$

$$kx = 6x$$

$$k = 6$$

_________________
"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: 13726
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.
_________________
Re: Let C and K be constants.If x^2+Kx+5 factors into (x+1)(x+C), then   [#permalink] 01 Oct 2018, 07:16
Display posts from previous: Sort by