help with 3 math problems. 10 points to best answer. Please need help.?

Question

1.Given the data points (2, 9), (-4, 8), and (7, 3), the relationship shows a direct variation
a.true
b,false

2.Given the equation of a line y = 2/5x - 2, the slope and y-intercept are respectively:
a.2, -2/5
b.-2, 2/5
c.2/5, 2
d. 2/5 , -2

3.Given the equation of a line, y = -1/3x , the slope and y-intercept are respectively:
A.-1/3, 0
b.1/3, 0
c. 3, 0
d. -3, 0

Answer 1

b.c,a

Answer 2

1) for this question, they are actually talking about gradient(or slope). Gradient is calculated simply by "Rise divided by Run" which is essentially the vertical height divided by the horizontal height.
How you calculate that and apply to this question is finding the gradient of any 2 points and comparing it with the gradient of the other 2 points, seeing if they are the ssame.

So in this case, lets just compare (2, 9) and (-4, 8) with (-4, 8) and (7, 3). You can play around with which sets of data points you want to comopare, but bear in mind that in your comparison, there has to be only one common data point.

To calculate gradient (or slope): we use the formula:
[y2 - y1] / [x2 - x1] where x and y are the respective numbers in the data points. If you think about it as a graph, you will find that you are essentially calculating distances when you apply the formula. ok ur set:

To calculate gradient for (2, 9) and (-4, 8): it is:
(8-9) / (-4-2) = 1 / (-6)
which gives you -(1/6). remember this number.

To calculate gradient for (-4, 8) and (7, 3) it is:
(3-8) / (7+4) = (-5) / (11)
which gives you -(5/11), which doesnt match the above number of -(1/6).
Note that it is 7 + 4 because you are taking 7 minus (-4) in the formula, thus giving you 7 + 4.

Thus since the gradients to not equate, the data points do NOT show a direct variation. answer is (b) false.

Qn 2) This is a simple example. Here's a simple formula for you to remember:
all straight line graphs are denoted by this universally:
y = mx + c, where:
*y is the y value
*x is the x value
*m is the gradient (or value of the slope)
*c is the y-intercept.

So just by looking at the equation you can easily solve for this question.

in this question, the slope m is 2/5 (just look at the number preceding the x), whilst the y-intercept c is -2. remember that you must always include the sign (either + or -) preceding the number.

so the answer is (d) 2/5, -2

Qn 3) this question is similar to question 2. in this case the y-intercept is zero whilst the slope is -(1/3) so the answer is:
(a) -1/3, 0.
this is because the equation given in the question is essentially:
y = -1/3 + 0

Final answer: 1(b); 2(d); 3(a).

Hope this helps. :D

Answer 3

(1) it is false,so the choice is (b
(2)slope is 2/5 and the y- intercept is -2,so the option (d)
(3)answer is -1/3 and 0,so the choice (a)

Answer 4

1. b
In order for it to be direct variation, the points should all line up.

2. d
The slope of a line is the number in front of the 'x' when written in slope-intercept form. The last number is the y-intecept.

3. a
Same reason as # 2.

Answer 5

2 points

Answer 6

1.false, 2.D, 3. A.

Answer 7

1. B

2. D
y=mx+b
m is always slope, b is y interceptD
3. A
b is just zero here.

Answer 8

1.false
...
for 2 and 3,
y=(slope)x+(y-intercept)
2.d
3.(a)

Answer 9

I could just give you the wrong answers,but that would be mean. GET A TUTOR OR ASK YOUR TEACHER!!! You are just uesing this site for math help!

Answer 10

b.
d.
a.
When you graph it out, you see the variation doesn't exist, "y=mx+b" where m=slope and b=the y-intercept

Answer 11

1)a
2)d
3)d