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Question 1158869: What is a y intercept and what purpose does it serve? (I am a not so mathematical Dad trying to help a challenged child)
Found 3 solutions by math_helper, Cromlix, Theo:
Answer by math_helper(2461)   (Show Source):
You can put this solution on YOUR website!
The y-intercept is where the line (or curve) crosses the y-axis. Mathematically, if you have y = some_function_of_x then it is the y value when you set x=0.
OPTIONAL:
For example, when dealing with straight lines, the equation of the line is often written y = mx + b where m=slope (the rise/run or (change in y) / (change in x)) and b is the y-intercept.
Below is the graph of y = 2x-5 in green. Notice how the line meets the y-axis at -5:
Answer by Cromlix(4381)  (Show Source):
You can put this solution on YOUR website! Hi there,
The equation of a line is y = mx + c
m = gradient or slope
c = the line's y intercept
Knowing the line's y intercept allows, with the x intercept, to work out the gradient or slope.
e.g. y = 4x + 8
To find where the line cuts the x axis make y = 0
0 = 4x + 8
4x = -8
x = -2 Cuts x axis at (-2, 0)
To find where line cuts the y axis make x = 0
y = 4x + 8
y = 4(0) + 8
y = 8 cuts y axis at (0, 8)
To find the gradient use y2 - y1/x2 - x1
Using the example y = 4x + 8, the y intercept (0, 8) (x1, y1) and the x intercept (-2, 0) (x2, y2)
y2 - y1/x2 - x1 = 0 - 8/-2 - 0 = -8/-2 = 4 The gradient (slope) in y = 4x + 8
Hope this helps, mate. :-)
Answer by Theo(13342)  (Show Source):
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