powerprep question

jc114 · Posted: Sat May 12, 2007 7:50 am Post subject: powerprep question

In the xy plane, at what two points does the graph of y= (x+a)(x+b) intersect the x axis?
(1) a+b=-1
(2) the graph intersects the x=axis at at (0,6)

i chose E but the answer is c

f2001290 · Posted: Sun May 13, 2007 5:31 am Post subject:

When a line intersects X axis, y = 0

1. y = x^2 + (a+b)x + ab - not sufficient

2. Substitute (0,6) in the equation, we get the value of ab.

Using both the statements

x^2 - x + 6 = 0

we can get two values of x by solving this equation

jc114 · Posted: Sun May 13, 2007 2:27 pm Post subject:

but then if there are 2 answers for x isn't it then E?

f2001290 · Posted: Mon May 14, 2007 4:42 am Post subject:

Read the question carefully, it asks for two points.

If x1 nad x2 are the values of x, then (X1,0) and (x2,0) are my points