Posted by **Scotty** on Wednesday, June 2, 2010 at 11:17am.

x2 + 3x - 18 < 0

A.(-6, 3)

B. (-3, 6)

c.(-∞, -6)∪(3, ∞)

D. (-∞, -3)∪(6, ∞)

- Algebra -
**Jen**, Wednesday, June 2, 2010 at 11:18am
Find two numbers that multiply to negative 18 and add to 3. (x+6)(x-3)

- Algebra -
**Scotty**, Wednesday, June 2, 2010 at 11:24am
thankyou but, so what would you say the answer is a,b,c or d?

- Algebra -
**MathMate**, Wednesday, June 2, 2010 at 12:43pm
If you sketch the curve f(x) = x²+6x-18=0, it will be concave upwards, which means that if the curve cuts the x-axis, the domain of the function f(x)<0 will be between the two roots of f(x)=0. Thus c and d are not appropriate answers.

Jen already factorized f(x)=(x+6)(x-3).

You will need to find the value of the roots (where the curve cuts the x-axis) and find the appropriate response.

If you need help understanding the interval notation, please post.

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