What is the y-intercept?

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by ankur.agrawal » Wed Sep 29, 2010 2:05 pm
qwe12 wrote:my way of solving this is as follows, if y = mx + c, is the equation of a line, where c is the y intercept.

from 1) m = 3c

=> y = 3cx + c, to determine the y intercept, plug y = 0

0 = c(3x + 1)

Here, we can 2 options c=0 and x can be anything
or 3x+1 = 0 and c can be anything.

NOT SUFFICIENT.

from 2)

y = m(-1/3) + c
y = -m/3 + c

so c = y + m/3, if y goes to 0, c = m/3, and m can be anything,

NOT SUFFICIENT.

Using (1) and (2) we find we have 2 equations and 3 unknowns.

y = 3cx + c
y = -m/3 + c

We need 3 equations to solve for 3 unknowns.

SO (E)
To determine the y intercept, plug y = 0 . Why? Is dere any rule relating to this?

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by imhimanshu » Mon Mar 05, 2012 6:08 am
To determine the y intercept, plug y = 0 . Why? Is dere any rule relating to this?
This is wrong. To determine y intercept, you need to plugin x=0 . Since y intercept is the point where line cuts y axis. Similarly for finding the x intercept, you need to put y =0.
Its an inverse relationship.
Let me know, if anything requires clarity