Notes
| \(\text{ Parabolas }\) |
|
\(\underline{\text{Vertex Form}}\) |
\(\underline{\text{Standard Form}}\) |
\(\underline{\text{Intercepts Form}}\) |
| \(\text{Equation}\) |
\(f(x)=a(x-h)^2+k\) |
\(f(x)=ax^2+bx+c\) |
\(f(x)=a(x-p)(x-q)\) |
| \(\text{Vertex}\) |
\((h,k)\) |
\(\left(\frac{-b}{2a},f\left(\frac{-b}{2a}\right)\right)\) |
\(\left(\frac{p+q}{2},f\left(\frac{p+q}{2}\right)\right)\) |
| \(\text{Axis of Symmetry}\) |
\(x=h\) |
\(x=\frac{-b}{2a}\) |
\(x=\frac{p+q}{2}\) |
| \(\text{Opening Direction}\) |
\( \text{ opens up if }a\gt0,
\text{ opens down if } a\lt0\) |
Problems
State the vertex, axis of symmetry and opening direction.
\(\textbf{1)}\) \(f(x)=3(x-4)^2+2\)
Hint:
This is vertex form \(\rightarrow f(x)=a(x-h)^2+k\)
Vertex \(\rightarrow (h,k)\)
Axis of Symmetry \(\rightarrow x=h\)
Direction of Opening \(\rightarrow \text{ opens up if }a\gt0, \text{ opens down if } a\lt0\)
The vertex is \( (4,2) \)
The axis of symmetry is \( x=4 \)
The opening direction is up
\(\textbf{2)}\) \(f(x)=-2(x+3)^2-1\)
The vertex is \( (-3,-1) \)
The axis of symmetry is \( x=-3 \)
The opening direction is down
\(\textbf{3)}\) \(f(x)=(x+5)^2-3\)
The vertex is \( (-5,-3) \)
The axis of symmetry is \( x=-5 \)
The opening direction is up
\(\textbf{4)}\) \(f(x)=4(x-4)^2\)
The vertex is \( (4,0) \)
The axis of symmetry is \( x=4 \)
The opening direction is up
\(\textbf{5)}\) \(f(x)=-x^2+3\)
The vertex is \( (0,3) \)
The axis of symmetry is \( x=0 \)
The opening direction is down
\(\textbf{6)}\) \(f(x)=2x^2-4x+5\)
Hint:
This is standard form \(f(x)=ax^2+bx+c, \,\,\,\)
Vertex \(=\rightarrow \left(\frac{-b}{2a},f\left(\frac{-b}{2a}\right)\right)\)
Axis of Symmetry \(\rightarrow x=\frac{-b}{2a}\)
Direction of Opening \(\rightarrow \text{ opens up if }a\gt0, \text{ opens down if } a\lt0\)
The vertex is \( (1,3) \)
The axis of symmetry is \( x=1 \)
The opening direction is up
\(\textbf{7)}\) \(f(x)=x^2-6x+3\)
The vertex is \( (3,-6) \)
The axis of symmetry is \( x=3 \)
The opening direction is up
\(\textbf{8)}\) \(f(x)=-x^2+4x+5\)
The vertex is \( (2,9) \)
The axis of symmetry is \( x=2 \)
The opening direction is down
\(\textbf{9)}\) \(f(x)=4x^2+8x-2\)
The vertex is \( (-1,-6) \)
The axis of symmetry is \( x=-1 \)
The opening direction is up
\(\textbf{10)}\) \(f(x)=-2x^2+8x-3\)
The vertex is \( (2,5) \)
The axis of symmetry is \( x=2 \)
The opening direction is down
\(\textbf{11)}\) \(f(x)=2(x-5)(x-1)\)
Hint:
This is intercept form \(f(x)=a(x-p)(x-q), \,\,\,\)
Vertex \(\rightarrow \left(\frac{p+q}{2},f\left(\frac{p+q}{2}\right)\right)\)
Axis of Symmetry \(\rightarrow x=\frac{p+q}{2}\)
Direction of Opening \(\rightarrow \text{ opens up if }a\gt0, \text{ opens down if } a\lt0\)
The vertex is \( (3,-8) \)
The axis of symmetry is \( x=3 \)
The opening direction is up
\(\textbf{12)}\) \(f(x)=-3(x+5)(x-3)\)
The vertex is \( (-1,48) \)
The axis of symmetry is \( x=-1 \)
The opening direction is down
\(\textbf{13)}\) \(f(x)=5(x)(x-4)\)
The vertex is \( (2,-20) \)
The axis of symmetry is \( x=2 \)
The opening direction is up
\(\textbf{14)}\) \(f(x)=-(x+7)(x+5)\)
The vertex is \( (-6,1) \)
The axis of symmetry is \( x=-6 \)
The opening direction is down
\(\textbf{15)}\) \(f(x)=4(x)(x-2)\)
The vertex is \( (1,-4) \)
The axis of symmetry is \( x=1 \)
The opening direction is up
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