SOLUTION: graph y=3x^2 -12x-3. Then state the vertex. Please help me with this.

Algebra ->  Graphs -> SOLUTION: graph y=3x^2 -12x-3. Then state the vertex. Please help me with this.      Log On


   

Question 981430: graph y=3x^2 -12x-3. Then state the vertex.
Please help me with this.
Found 2 solutions by josgarithmetic, macston:
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
Put into standard form and then try to graph.

y=3%28x%5E2-4x-1%29
Study the lesson on Completing The Square.
y=3%28x%5E2-4x%2B4-4-1%29
y=3%28%28x-2%29%5E2-5%29
highlight%28y=3%28x-2%29%5E2-15%29

Now you know the vertex, how the parabola is oriented, and can find the zeros.

graph%28300%2C300%2C-11%2C11%2C-16%2C6%2C3x%5E2-12x-3%29

Answer by macston(5194) About Me  (Show Source):
You can put this solution on YOUR website!
.
+graph%28+800%2C+800%2C+-15%2C+15%2C+-15%2C+15%2C+3x%5E2-12x-3%29+
.
Standard form: y=ax%5E2-bx%2Bc
.
y=3x^2-12x-3
.
x value of vertex:
x=-b%2F2a
x=-%28-12%29%2F%28%282%29%283%29%29
x=12%2F6
x=2
.
Use the x value in original equation to get y value.
.
y=3x%5E2-12x-3
y=3%282%5E2%29-12%282%29-3
y=12-24-3
y=-15
.
The vertex is (2,-15)