SOLUTION: How do you find the vertex and axis of symmetry of the graph of the function for these two problems: 1) g(x) = 4x squared - 48x + 7 2) j(x) = -2x squared + 21x - 7 Thanks.

Algebra ->  Graphs -> SOLUTION: How do you find the vertex and axis of symmetry of the graph of the function for these two problems: 1) g(x) = 4x squared - 48x + 7 2) j(x) = -2x squared + 21x - 7 Thanks.      Log On


   



Question 973513: How do you find the vertex and axis of symmetry of the graph of the function for these two problems:
1) g(x) = 4x squared - 48x + 7
2) j(x) = -2x squared + 21x - 7
Thanks.
Laura

Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
Convert into standard form and read the information from the result. This requires for your examples, completing the square.

(1):

g%28x%29=4x%5E2-48x%2B7
4%28x%5E2-12x%29%2B7
4%28x%5E2-12x%2B36%29%2B7-%2836%2A4%29
4%28x-6%29%5E2%2B7-144
4%28x-6%29%5E2-137

Vertex: (6,-137)
Axis of Symmetry: x=6

The reasoning for choose 36*4 to add and subtract is taught in this lesson:
http://www.algebra.com/my/Completing-the-Square-to-Solve-General-Quadratic-Equation.lesson?content_action=show_dev