Write the equation of the line passing through?

Question

Write the equation of the line passing through (0, –1) and (4, –21).

Answer 1

y = -5x -1


Doug

Answer 2

y=mx + c is the equation of a straight line....wooo
where m is the gradient or slope of the line and c is the constant.

First you...
let the point (0, -1) be (x1,y1)
let the point (4,-21) be(x2,y2)

then your two equations are
a. -1 = m(0) + c and
b. -21 = m(4) + c

that's not the answer, just saying how to solve it.

Edit:
you can do like that other guy or gal said or simply just having 2 equations with 2 unknows means u can solve as simultaneous equations.

From equation a. m*0=0 hence, c= -1 which you now enter into second equation
b.
-21=m(4) + - 1
-21=m(4) -1...moving -1 to other side it turns to +1 so

-21+1 = m(4)
-20=m*4
-20/4 =m
-5=m
so now m= -5 and c = -1 now enter those into the equation of a straight line
y=mx + c you get

y= -5x -1

tadaaa...i'm still a math wizz


What grade math is this anyways...i havent done this since...well a while.

umm..uummm you won't get the question right is you dont put it in terms of y=mx + c
so having 5x + y + 1 = 0 is wrong...sorry.

Answer 3

equation of line is y - y1 = m (x - x1)
where m is the slope and m = (y2 - y1) / (x2 - x1)
here (x1,y1) and (x2,y2) are the points
now if we apply this for the above points (0,-1) and (4,-21)

we have m = (-21+1)/(4-0) = -5
and equation is

y - (-1) = -5(x - 0)

by simplifying we get equation as

5x + y + 1 = 0