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Comment on px+qy+r
Hi Brent, for line questions
Is it safe to assume that the following equation: px+qy+r=0 implies that if it re-arranged as a slope/equation of a formula, it becomes :
px+qy+r=0 --> as an equation of a line --> y= -px/q +r/q
So my question is, will the GMAT test-makers ever try to throw in a trick where "x" in the given equation is actually y value and/or the "y" is actually the "x" value?
Implying that the equation would then become:
px+qy+r=0 --> as an equation of a line --> x= -qy/p + r/p
Thanks!
Almost!
Almost!
If a line is defined as px + qy + r = 0, then we can write: y = -px/q - r/q (you have + r/q)
Here, the slope = -p/q and the y-intercept = -r/q
To answer your other question, I've never seen an official GMAT question in which the x-axis and the y-axis are switched. In fact, the term "x-y coordinate plane" assumes that the x-axis is the horizontal axis, and the y-axis the vertical one.
Cheers,
Brent
Hi Brent, if I got y = -r/q -
That's correct.
That's correct.
Great to know and thanks
However positive slope and negative slope from this will mean the same in other areas of calculations as well ? or if any difference where will that be? Thanks Brent
Keep in mind that, from the
Keep in mind that, from the given equation, we know that the line's slope = -p/q, and the y-intercept = -r/q.
However, we can't conclude that, since the slope is equal to -p/q, the slope must be negative.
Just because it features a negative symbol, doesn't mean the value of -p/q is negative.
For example, if p = 6 and q = -2, then -p/q = -(6)/(-2) = 3
Great explanation and thanks