Question 110802


If you want to find the equation of line with a given a slope of {{{-7/2}}} which goes through the point ({{{0}}},{{{-2}}}), you can simply use the point-slope formula to find the equation:



---Point-Slope Formula---
{{{y-y[1]=m(x-x[1])}}} where {{{m}}} is the slope, and *[Tex \Large \left(x_{1},y_{1}\right)] is the given point


So lets use the Point-Slope Formula to find the equation of the line


{{{y--2=(-7/2)(x-0)}}} Plug in {{{m=-7/2}}}, {{{x[1]=0}}}, and {{{y[1]=-2}}} (these values are given)



{{{y+2=(-7/2)(x-0)}}} Rewrite {{{y--2}}} as {{{y+2}}}



{{{y+2=(-7/2)x+(-7/2)(-0)}}} Distribute {{{-7/2}}}


{{{y+2=(-7/2)x+0}}} Multiply {{{-7/2}}} and {{{-0}}} to get {{{0}}}


{{{y=(-7/2)x+0-2}}} Subtract 2 from  both sides to isolate y


{{{y=(-7/2)x-2}}} Combine like terms {{{0}}} and {{{-2}}} to get {{{-2}}} 

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Answer:



So the equation of the line with a slope of {{{-7/2}}} which goes through the point ({{{0}}},{{{-2}}}) is:


{{{y=(-7/2)x-2}}} which is now in {{{y=mx+b}}} form where the slope is {{{m=-7/2}}} and the y-intercept is {{{b=-2}}}


Notice if we graph the equation {{{y=(-7/2)x-2}}} and plot the point ({{{0}}},{{{-2}}}),  we get (note: if you need help with graphing, check out this <a href=http://www.algebra.com/algebra/homework/Linear-equations/graphing-linear-equations.solver>solver<a>)


{{{drawing(500, 500, -9, 9, -11, 7,
graph(500, 500, -9, 9, -11, 7,(-7/2)x+-2),
circle(0,-2,0.12),
circle(0,-2,0.12+0.03)
) }}} Graph of {{{y=(-7/2)x-2}}} through the point ({{{0}}},{{{-2}}})

and we can see that the point lies on the line. Since we know the equation has a slope of {{{-7/2}}} and goes through the point ({{{0}}},{{{-2}}}), this verifies our answer.