What is the vertex form of y=13x^2 +3x- 36 ?

1 Answer
Feb 1, 2016

vertex form: y=(x+3/26)^2-1881/52

Explanation:

1. Factor 13 from the first two terms.

y=13x^2+3x-36

y=13(x^2+3/13x)-36

2. Turn the bracketed terms into a perfect square trinomial.
When a perfect square trinomial is in the form ax^2+bx+c, the c value is (b/2)^2. Thus you divide 3/13 by 2 and square the value.

y=13(x^2+3/13x+(3/13x-:2)^2)-36

y=13(x^2+3/13x+9/676)-36

3. Subtract 9/676 from the perfect square trinomial.
You cannot just add 9/676 to the equation, so you must subtract it from the 9/676 you just added.

y=13(x^2+3/13x+9/676 color(red)(-9/676))-36

4. Multiply -9/676 by 13.
The next step is to bring -9/676 out of the brackets. To do this, multiply -9/676 by the a value, 13.

y=color(blue)13(x^2+3/13x+9/676)-36[color(red)((-9/676))*color(blue)((13))]

5. Simplify.

y=(x^2+3/13x+9/676)-36-9/52

y=(x^2+3/13x+9/676)-1881/52

6. Factor the perfect square trinomial.
The last step is to factor the perfect square trinomial. This will allow you to determine the coordinates of the vertex.

color(green)(y=(x+3/26)^2-1881/52)

:., the vertex form is y=(x+3/26)^2-1881/52.