In the xy-plane, at what two points does the graph of y = (x+a)(y+b) intersect the x axis?
1. A + b =1
2. The graph intersects the y-axis at (0,-6)
xy plane problem on gmat 2.0 exam
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If x= 0, y=ab/(1-a)-----(1)
y=0, x= -a -------------(2)
A)a+b=1
if we replace b=1-a in (1) we get y=-a
Hence no particular solution for this equation.
B)Cuts y axis at (0,-6)
It implies ab/(1-a)=-6
ab= -6(1-a)-----(3)
There are two variables and one equation. Hence no solution
But if we combine both of these
replace b=1-a in (3) we get a = -6
which means (C)
y=0, x= -a -------------(2)
A)a+b=1
if we replace b=1-a in (1) we get y=-a
Hence no particular solution for this equation.
B)Cuts y axis at (0,-6)
It implies ab/(1-a)=-6
ab= -6(1-a)-----(3)
There are two variables and one equation. Hence no solution
But if we combine both of these
replace b=1-a in (3) we get a = -6
which means (C)
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The question should read:
In the xy-plane, at what two points does the graph of y = (x+a)(x+b) intersect the x axis?
I posted an explanation here:
https://www.beatthegmat.com/coordinate-g ... 83293.html
In the xy-plane, at what two points does the graph of y = (x+a)(x+b) intersect the x axis?
I posted an explanation here:
https://www.beatthegmat.com/coordinate-g ... 83293.html
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y = x^2 + (a+b)x + ab => This is the equation of the curve. Solving for x will the values at which the curve intersects the x axis. Or this is the question rephrased. What are the values of x ?fangtray wrote:In the xy-plane, at what two points does the graph of y = (x+a)(x+b) intersect the x axis?
We don't know the value of product ab in the equation - INSUFF1. A + b =1
Substitute the point in the eqn, x = 0 and y = -6, we get ab = -6. We don't the value of (a+b) INSUFF2. The graph intersects the y-axis at (0,-6)
Together we can find the value of x.
IMO C.
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