Search 75,776 tutors
FIND TUTORS
Ask a question
0 0

Choose the equation below that represents the line passing through the point (-3, -1) with a slope of 4.

Tutors, please sign in to answer this question.

3 Answers

ya we will use the simple formula and put the points (-3,-1) in that formula y-y1 =m(x-x1)

so, here x1 =-3 and y1 =-1 and m=4 so, simply by putting the values we get...

y-(-1)=4(x-(-3))

y+1=4(x+3)

y=4x+12-1

y=4x+11

 

Hi Amy...  I'll add:

The slope is the x-coefficient, or x-multiplier.  From our sample problem, we know we have one term, 4x

We also know that when we have a set of points from a graph, then we have an x-y coordinate (location) that gives us both x and y at the same time (same place on the equation graph), and both can be plugged into the equation.  

Coordinates are usually given as (x, y), and from our sample we have x = -1, and y = -3.  Now we can just plug these into the standard y = mx + b format for a linear (straight line) equation:  -1 = 4(-2) + b.

"b" is the value y has when x = 0; you can think of it as a y-offset above or below zero, because if b = 0, then when x = 0, y would also = 0, and our line would pass through (0, 0).

(y = m(0) + 0;  y = 0).  We can find b by solving y=mx+b for b:  b = y - mx.  

In our sample, b = (-1) - (4)(-3);  b = -1 + 12, so b = +11.  Our final equation:  y = 4x + 11

To prove it:  y = 4(-3) + 11;  y = -12 + 11 = -1, which is the original y-coordinate  :-)

There is a formula well-known as the point-slope equation. It gives the equation of the line through a given point with a given slope. Here it is:

y - y1 = m(x - x1),

where (x1, y1) is the given point and m is the slope.

I hope this helps. If you would like more assistance, please feel free to ask. I or another tutor will be happy to assist you.