Question

find equation of the straight line passing through (2,-1), (4,3) I need step to find y-intercept. Please, help

Answer 1

I have y = 1/5 x + b . and don't know how to find b

Answer 2

How did you find the slope ?
I would do change in y divided by change in x

Answer 3

with (2,-1) and (4,3)
the y values are -1 and +3
change in y is -1 -3 = -4
the x values are 2 and 4
change in x is 2 -4= -2

change in y divided by change in x is -4/-2
that is not 1/5

Answer 4

yes, y =2x +b.

Answer 5

to find b, replace x and y with a point that you know is on the line.
you know both (2,-1) and (4,3) are on the line. pick one, and replace x and y in

y= 2x+b
with the numbers. "solve" for b.
can you do that ?

Answer 6

-1 = 2(2) +b ---> b = 5?

Answer 7

pretty close.
you get
-1 = 4 + b

if b is 5 you get -1= 4+5 or -1= 9 which is horribly wrong.

I would add -4 to both sides to solve for b

Answer 8

-5?

Answer 9

so y = 2x -5 ?

Answer 10

yes
-1 = 4 + b
add -4 to both sides
-1 - 4 = 4 - 4 + b
-5 = b

the answer is
y =2x-5

we can check it using the other point, (4,3)
if we got it right, (4,3) should work:
3 = 2*4-5 ??
3 = 8 - 5
3 = 3
yes, that worked.

Answer 11

one more question: how to sketch y =|x+1| -1?

Answer 12

you should post it as a new question.

Answer 13

why?

Answer 14

anyway, thanks a lot for the previous one