# Pre-Algebra

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This is about Reasoning Strategy, I really need help on this, I have a test tomorrow on it! Please help... Ok, here's what it says:

3a. What is the y-intercept of the trend line? (What do they mean???)
3b. Locate one other point on the trend line, then find the slope of the trend line (I don't know what they mean?)

• Pre-Algebra -

3a. The y intercept is the value of y where x equals zero (where the trend line intercepts the y axis).

3b. Pick any other point on the trend line (besides the y intercept) and compute the slope as the change in y divided by the change of x.

• Pre-Algebra -

ok, for 3b, I would need to divide any point in the x axis by a point on the y axis? Or is that wrong?

• Pre-Algebra -

3a. The y-intercept is found when you set x to = 0. The y-intercept is the point where the graph of the line crosses the y-axis.

SAMPLE:

In the equation y = 3x + 5, what is the y-intercept?

It is the point (0,5). Do you see number 5? That number represents the y-intercept when x = 0.

Don't trust me?

Here it is:

Let x = 0.

y = 3(0) + 5

y = 0 + 5

y = 5

So, y became 5 when we set x to = 0.

====================================

3b. Pick any two points on the line and find the slope of the line.

The slope is a numerical value that describes just how slanted a given line is.

Here is is an example of finding the slope of a line.

SAMPLE:

Given the points (3, 4) and (8, 9), find the slope.

The symbol for slope is the letter m.

Let m = slope.

We now subtract b from d and a from c.

(a,b) = (3,4)

(c,d) = (8,9)

m = (9 - 4)/(8 - 3)

m = 5/5

m = 1

The slope is 1.

Did you follow?

• Pre-Algebra -

Yep, thank you VERY much! Except that I don't really get 3a...

• Pre-Algebra -

P(2,0) Q(4,4)