Question

I need help with this

Answer 1

9514 1404 393

Answer:

  B.  3x^2 +11x -20 = 0

Step-by-step explanation:

For solutions p and q, the quadratic will be

  (x -p)(x -q) = 0

We notice that the leading coefficients of the offered answer choices are greater than 1, so it will be convenient to use a value that "clears fractions."

  (x -4/3)(x -(-5)) = 0

  3(x -4/3)(x +5) = 0 . . . . multiply by 3 to clear the fraction

  (3x -4)(x +5) = 0 . . . . . . clear the fraction

  3x(x +5) -4(x +5) = 0 . . use the distributive property

  3x^2 +15x -4x -20 = 0 . . . . use the distributive property again

  3x^2 +11x -20 = 0 . . . . collect terms

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The constant in the product of factors is the product of roots:

  (x -p)(x -q) = x^2 -(p+q)x +pq

Here, that would mean the constant would be (4/3)(-5) = -20/3.

If we compare the above quadratic to the standard form:

  ax^2 +bx +c = 0

we find that we can divide the standard form equation by 'a' to get ...

  pq = c/a

That is, c/a = -20/3, so we might start looking for an answer choice that has a leading coefficient of a=3 and a constant of c=-20.