Answer:
b=a √3
Step-by-step explanation:
Answer:
Given: 
, y =6
To prove: x =7
On substituting the value of y =6 in the equation 7y = 8x -14 to solve for x.
or
42 = 8x -14 ......[1]
Addition Property of equality states that you add the same number to both sides of an equation.
Add 14 to both sides in equation [1];
42+14 =8x -14+14
Simplify:
56 = 8x
or
8x =56 ......[2]
Division Property of equality states that you divide the same number to both sides of an equation.
Divide by 8 to both sides of an equation [2];
Simplify:
x =7 Hence proved!
A two Column proof:
Statement Reason
1. 7y = 8x -14 Given
y= 6
2. 7(6) = 8x -14 Substitution property
3. 42+14 = 8x Addition property of equality
4. 56 =8x Simplify
5. x =7 Division Property of equality
Given, (0,−2).
Since the x-coordinate is 0, the point clearly lies on y-axis.
Also, the y-coordinate −2 being negative, the point lies on the negative y-axis.
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.
