Exercise 59 Page 63

We want to draw the graph of the given quadratic function. To do so, we will rewrite it in vertex form, f(x)=a(x-h)^2+k, where a, h, and k are either positive or negative numbers. f(x)=-2(x-3)^2 ⇕ f(x)=-2(x-3)^2+0 To draw the graph, we will follow four steps.

1. Identify the constants a, h, and k.
2. Plot the vertex (h,k) and draw the axis of symmetry x=h.
3. Plot any point on the curve and its reflection across the axis of symmetry.
4. Sketch the curve.

   Let's get started.

   Step 1

   We will first identify the constants a, h, and k. Recall that if a<0, the parabola will open downwards. Conversely, if a>0, the parabola will open upwards. Vertex Form:& f(x)= a(x- h)^2+k Function:& f(x)= -2(x- 3)^2+ We can see that a= -2, h= 3, and k= . Since a is less than 0, the parabola will open downwards.

   Step 2

   Let's now plot the vertex ( h,k) and draw the axis of symmetry x= h. Since we already know the values of h and k, we know that the vertex is ( 3, ). Therefore, the axis of symmetry is the vertical line x= 3.

   

   Step 3

   We will now plot a point on the curve by choosing an x-value and calculating its corresponding y-value. Let's try x=1.
   f(x)=-2(x-3)^2

   Substitute

   x= 1

   f( 1)=-2( 1-3)^2

   ▼

   Simplify right-hand side

   SubTerm

   Subtract term

   f(1)=-2(-2)^2

   CalcPow

   Calculate power

   f(1)=-2(4)

   MultNegPos

   (- a)b = - ab

   f(1)=-8
   When x=1, we have y=- 8. Thus, the point (1,- 8) lies on the curve. Let's plot this point and reflect it across the axis of symmetry.
   

   Note that both points have the same y-coordinate.

   Step 4

   Finally, we will sketch the parabola which passes through the three points. Remember not to use a straightedge for this!