Step 1: Analyze the given information and graph.
The parabola is g(x)=ax2+q.
The straight line is f(x)=mx+c.
R and S(2; 0) are the x-intercepts of g.
T(0; 8) is the y-intercept of g.
Graph f passes through R and T.
Since g(x)=ax2+q is a parabola with its axis of symmetry at x=0 (the y-axis), and S(2; 0) is an x-intercept, the other x-intercept R must be symmetric to S with respect to the y-axis. Therefore, R is (-2; 0).
T(0; 8) is the y-intercept of g. For a parabola of the form ax2+q, the y-intercept is also the vertex. Since the parabola has x-intercepts and the vertex is above the x-axis, it opens downwards.
5.1: Write down the range of g.
The vertex of g(x)=ax2+q is at (0,q). From the graph, T(0, 8) is the vertex. Since the parabola opens downwards, the maximum value of g(x) is the y-coordinate of the vertex.
The maximum value is y=8.
The range of g is all real numbers less than or equal to 8.
Rangeofg:yβ€8
5.2: Write down the x-coordinate of R.
As established in Step 1, due to the symmetry of g(x)=ax2+q about the y-axis, and S(2; 0) being an x-intercept, R must be the symmetric x-intercept.
xβcoordinateofR:β2
5.3: Calculate the values of a and q.
From T(0; 8) being the y-intercept of g(x)=ax2+q, we substitute x=0 and g(x)=8:
8=a(0)2+q
8=q
So, q=8. The equation for g(x) is now g(x)=ax2+8.
We use an x-intercept, for example S(2; 0), to find a. Substitute x=2 and g(x)=0:
0=a(2)2+8
0=4a+8
4a=β8
a=4β8β
a=β2
The values are a=β2 and q=8.
a=β2,q=8
5.4: Determine the equation of f.
The function f(x)=mx+c is a straight line that passes through R(-2; 0) and T(0; 8).
First, calculate the slope m:
m=x2ββx1βy2ββy1ββ=0β(β2)8β0β=28β=4
Next, find the y-intercept c. Since T(0; 8) is a point on the line and its x-coordinate is 0, the y-coordinate 8 is the y-intercept.
So, c=8.
The equation of f is f(x)=4x+8.
f(x)=4x+8
5.5: Use the graphs to determine the value(s) of x for which:
5.5.1: f(x)=g(x)
This condition means finding the x-coordinates where the graphs of f and g intersect. From the graph, the intersection points are R and T.
R has x-coordinate -2.
T has x-coordinate 0.
x=β2Β orΒ xΒ =Β 0
5.5.2: xβ
g(x)β€0
We know g(x)=β2x2+8. The x-intercepts of g(x) are x=β2 and x=2.
The parabola g(x) is above the x-axis (i.e., g(x)β₯0) for xβ[β2,2].
The parabola g(x) is below the x-axis (i.e., g(x)β€0) for xβ(ββ,β2]βͺ[2,β).
We need xβ
g(x)β€0. This occurs when:
- xβ€0 AND g(x)β₯0: This means xβ(ββ,0] and xβ[β2,2]. The intersection is xβ[β2,0].
- xβ₯0 AND g(x)β€0: This means xβ[0,β) and xβ(ββ,β2]βͺ[2,β). The intersection is xβ[2,β).
Combining these two cases, the solution is xβ[β2,0]βͺ[2,β).
xβ[β2,0]βͺ[2,β)
5.6: The graph h is obtained when g is reflected along the line y=0. Write down the equation of h in the form h(x)=px2+k.
Reflecting a function y=g(x) along the line y=0 (the x-axis) means that the new y-values are the negative of the original y-values. So, h(x)=βg(x).
We found g(x)=β2x2+8.
h(x)=β(β2x2+8)
h(x)=2x2β8
This is in the form h(x)=px2+k, where p=2 and k=β8.
h(x)=2x2β8
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