GMAT Prep Graph Question

[ssy]

Another GMAT prep question...can someone explain the answer please?

In the XY plane, at what 2 points does the graph of y=(x+a)(x+b) intersect the x-axis?

1) a+b = -1

2)Graph intersects y axis at (0, -6)

Answer is C, both statements are sufficient.

[jangojess]

ssy....pls keep the ans in spoiler when post any Qs...

here we need to find the at what point the equation intersect x-axis, which means we need to find the solution of (x+a)(x+b) = 0 (y will be 0 when equation intersects at x-axis). we need to find the values of a and b to get the actual solutions of the equation...

stmt 1 - a+b = -1..insuff to get values of a and b.

stm 2 - the graph intersects y-axis at (0,-6)...so substitue the values of y and x in the equation and we get ab = -6...still insuff to get what a and b are....

both - a+b = -1 and ab = -6..from both we can a and b...So suff...ans is C

[ssy]

Thanks again JangoJess!

How do I put the answer in a spoiler?

[beatthegmat]

When writing a post, you will see a button toward the right-hand side that says 'Spoiler'. Highlight some text that you want to hide and hit this button.

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