SOLUTION: Write a quadratic function in standard form with zeros 6 and -8?

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: Write a quadratic function in standard form with zeros 6 and -8?       Log On


   



Question 548218: Write a quadratic function in standard form with zeros 6 and -8?
Found 2 solutions by nerdybill, mathie123:
Answer by nerdybill(7384) About Me  (Show Source):
You can put this solution on YOUR website!
Write a quadratic function in standard form with zeros 6 and -8?
A zero at 6 means a factor of
(x-6)
A zero at -8 means a factor of
(x+8)
.
the function must then be:
(x-6)(x+8)
x^2+8x-6x-48
x^2+2x-48

Answer by mathie123(224) About Me  (Show Source):
You can put this solution on YOUR website!
We know if the quadratic function has zeros 6 and -8 then
x-6 and x-(-8)=x+8 are both factors of the quadratic function This means that
y=%28x-6%29%28x%2B8%29
Now... standard form is also known as vertex form and is written as
y=a%28x-h%29%5E2%2Bk

We can expand our quadratic from above and then put it into this form:
y=%28x-6%29%28x%2B8%29
y=x%5E2%2B8x-6x-48
y=x%5E2%2B2x-48
Now we must complete the square to get it into standard form. To do this, we must add half of the b value squared ((half of 2 is 1 and 1 squared is 1 so we add one). If we add 1, we must subtract it as well (so we are essentially not changing the equation).
y=x%5E2%2B2x-48
y=x%5E2%2B2x%2B1-48-1
Now taking the first three terms, they can be factored as so:
y=%28x%2B1%29%5E2-48-1
y=%28x%2B1%29%5E2-49
there we have it:)
Let me know if you are unsure about anything and I will make sure it is clear for you :)