SOLUTION: A parabola has equation y = 4x? + x + c. One x-intercept is -3. What is the value of c.

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Question 1202233: A parabola has equation y = 4x? + x + c. One x-intercept is -3. What is the value of c.
Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39617)   (Show Source): You can put this solution on YOUR website!
if this is for parabola.

Your given x intercept:

Solve this for c.
Answer by ikleyn(52786)   (Show Source): You can put this solution on YOUR website!
.
A parabola has equation y = 4x^2 + x + c.
One x-intercept is -3. What is the value of c ?
~~~~~~~~~~~~~~~~~~~~~~~ 

The condition says that if x= -3, then y = 0.

Let's write it as an equation

    0 = 4*(-3)^2 + (-3) + c

or, simplifying

    0 = 4*9 - 3 + c

    0 = 36 - 3 + c

    0 = 33 + c

    c = -33.


ANSWER.  c = -33.


CHECK.  So, we found out the the function is y = 4x^2 + x - 33.

        Let's substitute x= -3 in it.  You will get

        y = 4*(-3)^2 + (-3) - 33 = 4*9 - 3 - 33 = 36 - 3 - 33 = 0.   ! Correct !

The problem is just solved.

Please write me if you do understand this solution in full.



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