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July 22, 2014

July 22, 2014

Posted by **caduceus** on Friday, November 8, 2013 at 10:11pm.

"What is the equation of the line, in slope-intercept form, that goes through the point (-1, -8) with m = 3 ?"

here's my work:

y + 8 = -3(x + 1) [i put the values into the equation.]

y = -3x + 5 [i multiplied -3 by 1 and added 8 to both sides.]

is this right? my main question is whether or not i would add or subtract 8 in this situation. i know that y - (-8) is exactly the same as y + 8, so, in that case, would i subtract 8 from both sides?

- algebra -
**Kuai**, Friday, November 8, 2013 at 10:39pmy = mx + b

-8 = (3)(-1) + b

-8 = -3 + b

-8 + 3 = -3 + 3 + b

b = -5

y = 3x -5

- algebra -
**caduceus**, Friday, November 8, 2013 at 10:45pmunfortunately, y = 3x -5 is not an answer. here are my option:

A. y = -3x + 11

B. y = -3x + 5

C. y = -3x - 11

D. y + 1 = -3(x + 8)

- algebra -
**caduceus**, Friday, November 8, 2013 at 10:46pmthis is slope intercept form: y - y1 = m(x-x1)

- algebra -
**caduceus**, Friday, November 8, 2013 at 10:47pmoh wait nevermind, oops, that is not slope intercept form

- algebra -
**Kuai**, Friday, November 8, 2013 at 11:14pm(-1, -8)

m = 3

y -y1 = m (x -x1)

y -(-8) = 3 ( x - (-1))

y + 8 = 3(x + 1)

y + 8 = 3x + 3

y + 8 - 8 = 3x + 3 -8

y = 3x -5

Slope intercept form

y = mx + b

- algebra -
**Reiny**, Saturday, November 9, 2013 at 8:39amThe problem is the slope.

All the options indicate a slope of -3, but you stated the slope to be +3

Kuai's solution is correct according to the data supplied.

- algebra -
**caduceus**, Saturday, November 9, 2013 at 7:04pmoops, sorry!

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