SOLUTION: Find a formula for the linear function whose graph intercepts the x-axis at x=80 and the y-axis at y= -90

Question 1025727: Find a formula for the linear function whose graph intercepts the x-axis at x=80 and the y-axis at y= -90
Found 3 solutions by Cromlix, FrankM, josmiceli:
Answer by Cromlix(4381)   (Show Source): You can put this solution on YOUR website!
Hi there,
Using the co-ordinates (80,0)
and (0, -90)
Gradient = y2 - y1/x2 - x1
Gradient = 0 -(-90)/80 - 0
Gradient = 90/80 = 9/8
m = 9/8
Intercept with y axis = (0,-90)
therefore c = -90
y = mx + c
y = 9/8x - 90
Hope this helps :-)
Answer by FrankM(1040)   (Show Source): You can put this solution on YOUR website!
This problem is easily solved using standard form -
Ax+By=C
First C is the LCM, least common multiple of 80 and 90, which is 720.
Now Ax+By=720
When x=0, By=720, B(-90)=720 , and B is -8
When y=0, Ax=720, A(80)=720 , and A is 9
9x-8y=720
There are longer ways to solve. You have an intercept and can calculate a slope, etc. This is the fastest, and you can rearrange if other form is required.
Answer by josmiceli(19441)   (Show Source): You can put this solution on YOUR website!
Define the points of intersection:
x-intercept: ( 80,0 )
y-intercept: ( 0, -90 )
--------------------
Use the general point-slope formula

multiply both sides by

--------------------
check answer:
does it go through ( 80,0 ) ?

OK
does it go through ( 0, -90 ) ?

OK
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