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23 votes
23 votes
Identify the vertex, axis of symmetry, and min/max value of each.

User RBT
by
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1 Answer

12 votes
12 votes

we have the function

f(x)=3x^2-54x+241

this is a vertical parabola open upward (because the leading coefficient is positive)

the vertex is a minimum

Convert the quadratic equation into vertex form

y=a(x-h)^2+k

where

(h,k) is the vertex

and the axis of symmetry is equal to the x-coordinate of the vertex

so

x=h

step 1

Factor the leading coefficient


\begin{gathered} f(x)=3(x^2-18x)+241 \\ \text{complete the squares} \\ f(x)=3(x^2-18x+9^2-9^2)+241 \\ f(x)=3(x^2-18x+9^2)+241-(9^2)\cdot(3) \\ f(x)=3(x^2-18x+81)+241-243 \\ \text{rewrite as p}\operatorname{erf}ect\text{ squares} \\ f(x)=3(x-9)^2-2 \end{gathered}

the vertex is the point (9,-2)

the axis of symmetry is x=9

the vertex represent a minimum

User Michael Aubert
by
3.1k points