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.
It's a slope-intercept form where a slope = -1.5 and y-intercept = 3.
x - intercept: y = 0
Therefore we have the equation:
-1.5x + 3 = 0 |-3
-1.5x = -3 |:(-1.5)
x = 2
Answer: x-intercept = 2, y-intercept = 3
Number 6 is 10:10 The first plane arrives at 6:50 you add 50 minutes to that and keep adding 50 minutes until you get to after 10:00 because it says his plane arrived after 10:00.
Consecutive terms in an arithmetic sequence differ by a constant
. So
Denote the
-th term in the sequence by
. Now that
, we have
which means
Answer:
3 ≥ x
Step-by-step explanation:
