Find the vertex and axis of symmetry of the graph of the function.
-$f ( x ) = x ^ { 2 } + 4 x$
A) $( - 2 , - 4 ) ; x = - 2$
B) $( 2 , - 4 ) ; x = 2$
C) $( - 4,2 ) ; x = - 4$
D) $( 4 , - 2 ) ; x = 4$

Question

Quizplus · Accepted Answer

The vertex form of a quadratic function is $f(x) = a(x - h)^2 + k$, where $(h, k)$ is the vertex. To find the vertex of $f(x) = x^2 + 4x$, complete the square: $f(x) = (x^2 + 4x + 4) - 4 = (x + 2)^2 - 4$, so the vertex is $(-2, -4)$. The axis of symmetry is $x = h$, which is $x = -2$.

Find the Vertex and Axis of Symmetry of the Graph f(x)=x2+4xf ( x ) = x ^ { 2 } + 4 xf(x)=x2+4x

Find the Vertex and Axis of Symmetry of the Graph $f ( x ) = x ^ { 2 } + 4 x$