Algebra

x2 + 3x - 18 < 0

A.(-6, 3)

B. (-3, 6)

c.(-∞, -6)∪(3, ∞)

D. (-∞, -3)∪(6, ∞)

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  3. 👁 85
asked by Scotty
  1. Find two numbers that multiply to negative 18 and add to 3. (x+6)(x-3)

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    posted by Jen
  2. thankyou but, so what would you say the answer is a,b,c or d?

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    posted by Scotty
  3. 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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    posted by MathMate

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