## tina-ann 4 years ago solve the system of equations by graphing, f(x)=-1/2x +2 g(x)=9/2x -8

1. 3lroy

ok

2. 3lroy

let me see

3. tina-ann

4. 3lroy

but its pretty simple

5. tina-ann

6. dumbcow

is this correct f(x) = -(1/2)x + 2 f(x) = (9/2)x - 8

7. tina-ann

not sure how to make the fraction symbols for -1/8 and 9/2

8. dumbcow

thats ok me neither. both of these are linear of the form y = mx+b m = slope (rise/run) b = y-intercept (where it crosses y-axis) Now we need to graph each one First identify y-intercept for our first point 1) b = 2 2) b = -8 put these points on the graph on the y-axis

9. dumbcow

Next we look at slope to find second point 1) m = -1/2 This means starting at our y-intercept we go down 1 and over to right 2, repeat process for additional points 2) m=9/2 This means starting at y-intercept go up 9 and over to right 2 connect points to make each line point where they intersect is the solution

10. tina-ann

in the begining the first points b=2 b=-8 is that graphed as (2,-8)?

11. dumbcow

oh sorry i meant 1) to mean line 1 and 2) to mean line 2 they are separate points the x value is always zero for the y-intercept (0,2) (0,-8)

12. tina-ann

ok im really bad at this stuff

13. dumbcow

when you think y-intercept, think y-axis....points will be directly on y-axis

14. tina-ann

ok, so back to m=-1/2 and m=9/2

15. dumbcow

yes start with the first one go to starting point (0,2) -1 means go down 1 2 means go right 2 plot a point

16. tina-ann

ok so after i graphed them i came up with (2,1)?

17. dumbcow

correct this is the point where they cross

18. tina-ann

ok do u have time to help me with more

19. dumbcow

for a little bit, if nothing else i'll give you the steps

20. tina-ann

ok f(x)=-1/8x-3 g(x)=5/8x-9

21. dumbcow

same thing solve by graphing

22. dumbcow

do the exact same steps we did before the only thing that changes is the slope and y-intercept

23. dumbcow

for f(x) = mx + b m=-1/8 b=-3

24. dumbcow

can you graph the first point from there

25. tina-ann

start at 0 and go down the y to -3

26. dumbcow

good

27. tina-ann

same for (0,-8)

28. tina-ann

they intercept at (2,-3) is that correct?

29. dumbcow

careful the -8 was part of the slope for the first line

30. dumbcow

the other y-intercept would be (0,-9)

31. tina-ann

right , after i graphed them i got (2,-3)

32. dumbcow

remember what the difference between m and b are another way to think of it is the slope is always the number associated with the x, y-intercept is always the constant value

33. dumbcow

no you should get (8,-4)

34. dumbcow

starting at (0,-3) go down 1 over right 8

35. tina-ann

ok i got it

36. dumbcow

ok good keep repeating those steps gotta go good luck

37. tina-ann

thank you so much

38. dumbcow