Answer:
Step-by-step explanation:
5x + 9y = -11
3x + 9y = -3
5x + 9y = -11
-3x - 9y = 3
2x = -8
x = -4
-12 + 9y = -3
9y = 9
y = 1
(-4, 1)
Answer is C
Answer:
x = 2 and x = 10
Step-by-step explanation:
(x+3)^2 = (x - 5)^2 + (x + 2)^2
x^2 + 6x + 9 = x^2 - 10x + 25 + x^2 + 4x + 4
x^2 + 6x + 9 =2x^2 - 6x + 29
x^2 - 12x + 20 = 0
(x - 10)(x - 2) = 0
x - 10 = 0; x = 10
x - 2 = 0; x = 2
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.
Answer:
9m⁸
Step-by-step explanation:
3^2=9
(m⁴)² = m⁸
9*m⁸
