For this case we have that by definition, the equation of the line of the slope-intersection form is given by:
Where:
m: It is the slope of the line
b: It is the cut-off point with the y axis.
According to the data of the statement we have the following points:
We found the slope:
Thus, the equation is of the form:
We substitute one of the points and find b:
Finally, the equation is:
Answer:
27 has to be C
I can't see the whole question for 28 and 29
OK, so the graph is a parabola, with points x=0,y=0; x=6,y=-9; and x=12,y=0
Because the roots of the equation are 0 and 12, we know the formula is therefore of the form
y = ax(x - 12), for some a
So put in x = 6
-9 = 6a(-6)
9 = 36a
a = 1/4
So the parabola has a curve y = x(x-12) / 4, which can also be written y = 0.25x² - 3x
The gradient of this is dy/dx = 0.5x - 3
The key property of a parabolic dish is that it focuses radio waves travelling parallel to the y axis to a single point. So we should arrive at the same focal point no matter what point we chose to look at. So we can pick any point we like - e.g. the point x = 4, y = -8
Gradient of the parabolic mirror at x = 4 is -1
So the gradient of the normal to the mirror at x = 4 is therefore 1.
Radio waves initially travelling vertically downwards are reflected about the normal - which has a gradient of 1, so they're reflected so that they are travelling horizontally. So they arrive parallel to the y axis, and leave parallel to the x axis.
So the focal point is at y = -8, i.e. 1 metre above the back of the dish.
Both Aliyah and Ivan are correct because both chose the correct scale factor for the dilation and both describe other transformations that would produce triangle <span>. </span>
