Author 
Message 
TAGS:

Hide Tags

Intern
Joined: 25 Apr 2015
Posts: 4

Does the line with equation ax + by = c, where a, b and c are real con
[#permalink]
Show Tags
04 May 2016, 10:18
Question Stats:
65% (00:55) correct 35% (01:44) wrong based on 237 sessions
HideShow timer Statistics
Does the line with equation ax + by = c, where a, b and c are real constants, cross the xaxis? (1) b ≠ 0 (2) ab > 0 Hi guys!
I took recently Exam 5 (from Gmat Prep Exam Pack 2) and I'm struggling with the following question:
Here is my solution: I solved the equation for y, so that I got y=ax/b + c/b. If the line crosses the xaxis, then there should be a point on it with coordinates (0,y) or otherwise, y=c/b Therefore, b is not allowed to be 0 ( Statement 1) and there must be y, such that it is c/b (i don't have this information). Hence, my solution is E. However, this is not the official answer ...
Official Answer and Stats are available only to registered users. Register/ Login.



Intern
Joined: 01 Jan 2015
Posts: 31
Location: India
GPA: 3.71
WE: Consulting (Retail Banking)

Re: Does the line with equation ax + by = c, where a, b and c are real con
[#permalink]
Show Tags
04 May 2016, 10:36
if b is not equal to zero then if a equal to zero then it will definitely not pass by x axis where as when a is non zero may pass so 1st statement is not sufficient. if ab>0 the either both are positive or both are negative also non of them as zero. Hench there will always be ax+by hence always a slope(a/b) and if a line always has slope it will always pass through x axis. So the answer can be given only by statement 2 hence B is the answer.
_________________
_________________ "Kudos please "



Intern
Joined: 05 May 2016
Posts: 2
Location: Israel

Re: Does the line with equation ax + by = c, where a, b and c are real con
[#permalink]
Show Tags
05 May 2016, 12:09
aishkar wrote: if b is not equal to zero then if a equal to zero then it will definitely not pass by x axis where as when a is non zero may pass so 1st statement is not sufficient. if ab>0 the either both are positive or both are negative also non of them as zero. Hench there will always be ax+by hence always a slope(a/b) and if a line always has slope it will always pass through x axis. So the answer can be given only by statement 2 hence B is the answer. Fix me if i'm wrong:Generally, we can say that if b=0, then the slope is infinite and will definitely cross the x axis (straight vertical line). Also we can say that if ax+c=0 the line will never pass through the x axis (straight horizontal line). Am i right about that subject?
_________________
IMPOSSIBLE IS NOTHING!



Manager
Joined: 17 Sep 2015
Posts: 95

Re: Does the line with equation ax + by = c, where a, b and c are real con
[#permalink]
Show Tags
08 May 2016, 21:00
by = ax + c y = (a/b)*x + c/b if x = 0, then y = c/b and if y = 0, then (a/b)*x = c/b x = c/a........., we need a!= 0 this is valid only in B) Hence B is the ans.....can someone confirm this?
_________________
You have to dig deep and find out what it takes to reshuffle the cards life dealt you



Manager
Joined: 18 May 2016
Posts: 67
Concentration: Finance, International Business
GPA: 3.7
WE: Analyst (Investment Banking)

Re: Does the line with equation ax + by = c, where a, b and c are real con
[#permalink]
Show Tags
06 Jun 2016, 11:25
aniketm.87@gmail.com wrote: by = ax + c
y = (a/b)*x + c/b
if x = 0, then y = c/b
and if y = 0, then
(a/b)*x = c/b
x = c/a........., we need a!= 0
this is valid only in B) Hence B is the ans.....can someone confirm this? I am wasn't sure what you meant in the last line with a!=0 My thinking for the last line following your method: We know that x = \(\frac{c}{a}\) The question is asking us: Is there a value x for when y equals 0? The only circumstance when x = \(\frac{c}{a}\) will not have an actual value is if a = 0,then the answer is undefined and there is not value of x for when y = 0. Thus, Stem 2 tells us that a*b > 0, which means they are both positive or negative and thus, there will always be a value of x when y = 0. Hope it helps!
_________________
Please kindly +Kudos if my posts or questions help you!
My debrief: Selfstudy: How to improve from 620(Q39,V36) to 720(Q49,V39) in 25 days!



Senior Manager
Joined: 02 Mar 2012
Posts: 334

Re: Does the line with equation ax + by = c, where a, b and c are real con
[#permalink]
Show Tags
07 Jun 2016, 01:03
B
to NOT cross x axis constant a=0
1)nothing about a is given . a=0 or a is not eq to 0
2)ab>0 a,b =+ve or a,b+ve but surely not 0. that means line can have either +ve or ve slope. Suff
hope it helps



Retired Moderator
Joined: 05 Jul 2006
Posts: 1734

Re: Does the line with equation ax + by = c, where a, b and c are real con
[#permalink]
Show Tags
07 Oct 2016, 08:34
dgeorgie wrote: Hi guys!
I took recently Exam 5 (from Gmat Prep Exam Pack 2) and I'm struggling with the following question:
Does the line with equation ax+by=c, where a,b and c are real constants, cross the xaxis? (1) b ≠ 0 (2) ab>0
Here is my solution: I solved the equation for y, so that I got y=ax/b + c/b. If the line crosses the xaxis, then there should be a point on it with coordinates (0,y) or otherwise, y=c/b Therefore, b is not allowed to be 0 ( Statement 1) and there must be y, such that it is c/b (i don't have this information). Hence, my solution is E. However, this is not the official answer ... the question asks whether the line is parallel to x axis or not slope = a/b if = 0 then line is parallel if not then it definitely crosses the x axis from1 ...no idea about a .... insuff from 2 neither a nor b is 0 and they have the same sign thus slope is ve and ll defo cross the x axis B



Intern
Joined: 30 May 2017
Posts: 41

Re: Does the line with equation ax + by = c, where a, b and c are real con
[#permalink]
Show Tags
13 Jan 2018, 02:57
I took recently Exam 5 (from Gmat Prep Exam Pack 2) and I'm struggling with the following question:
Does the line with equation ax+by=c, where a,b and c are real constants, cross the xaxis? (1) b ≠ 0 (2) ab>0
Here is my solution: I solved the equation for y, so that I got y=ax/b + c/b. If the line crosses the xaxis, then there should be a point on it with coordinates (0,y) or otherwise, y=c/b Therefore, b is not allowed to be 0 ( Statement 1) and there must be y, such that it is c/b (i don't have this information). Hence, my solution is E. However, this is not the official answer ...
Hi,
If the line crosses x axis then there must be a point (x,0) not (0,y) as assumed by you.




Re: Does the line with equation ax + by = c, where a, b and c are real con &nbs
[#permalink]
13 Jan 2018, 02:57






