Answer:
6x-6
Step-by-step explanation:
The Distributive property says that a(b+c) = ab+ac
In my example you distribute the value on the outside to the things on the inside
In your problem you have a two on the outside that needs to be distributed to a 3x and a -3
1) 2 multiplied by 3x equals 6x giving you the first part of your answer!
2) 2 multiplied by -3 equals -6 giving you the second part of your answer!
Don't forget that there is a - sign between the 3x and 3, don't drop it!
Put the two values together to get 6x-6
Let me know if you have any further questions :)
Answers:
8. 12x+3= 27
move 3 to the other side , sign changes from +3 to -3
12x+3-3=27-3
12x= 24
divide by 12 for both sides
12x/12=24/12
x= 2
9. 6(y-10)=42
mutiply the bracket by 6
(6)(y)(6)(-10)= 6y-60
6y-60= 42
move -60 to the other side, sign changes from -60 to +60
6y-60+60=42+60
6y=102
divide by 6
6y/6=102/6
y=17
10. 9x-2=4x+13
move +4x to the other side
9x-4x-2= 4x-4x+13
5x-2= 13
5x-2+2= 13+2
5x= 15
divide by 5 for both sides
5x/5= 15/5
x= 3
11. 4/3y+5/2y= 1
find the common denominator for both of the fractions which is 6.
Mutiply by 2 for 4/3y .
4(2)/3(2)y=8/6y
Mutiply by 3 for 5/2y
5(3)/2(3y)= 15/6y
8/6y+15/6y= 23/6y
23/6y= 1
Mutiply both sides by 6/23
23/6y(6/23)= 1 (6/23)
Cross out 6 and 6 , divide by 6 and then becomes 1.
Cross out 23 and 23, divide by 23 and then becomes 1.
1*1*y=y
y= 6/23
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:
the answers are A D and E
