posted by Gabby on .
Part 1: When writing linear equations, how do you determine which form of a line to use?
Part 2: Choose 1 set of points from the choices below. Then, solve the problem and post your solution, showing your steps.
Write an equation in point-slope form for the line that passes through one of the following pairs of points (you may choose the pair you want to work with). Then, use the same set of points to write the equation in standard form and again in slope-intercept form.
(5, 1), (–3, 4)
(0, –2), (3, 2)
(–2, –1), (1, 2)
Part 3: View and comment on the work of at least 2 other students. If possible, choose students' whose work is based on different sets of points from the ones you chose.
I need help from Steve and or Reiny, I've done work similar to this but not this.....
Different texts use slightly different names for the form of the linear equation.
4x + 3y -12 = 0 -----> I would call general form
4x + 3y = 12 -------> standard form
y = (-4/3)x + 4 ---- > slope-y intercept form
point-slope form is a starting equation, usually ending up with one of the above.
Which ever method you use, finding the slope is a good start.
I will do the first one:
2 points (5,1) and (-3,4)
slope = (4-1)/(-3-5) = 3/-8 or -3/8
y-1 = (-3/8)(x-5) from y - y1 = m(x - x1)
at this point multiply each side by the denominator of the slope, if the slope is a fraction
8y - 8 = -3(x-5)
your fractions have disappeared, yeahhh!
8y - 8 = -3x + 15
3x + 8y = 23
at this stage I use the point that was not used and test if it satisfies my equation.
LS = 3(-3) + 8(4) = -9+32 = 23
RS = 23 , all is good!
Once you have the equation is the simple form of
3x + 8y = 23, you can go to any of the others
changing it to slope - y intercept form takes 2 steps
1. keep only the y term on the left side
3x + 8y = 23 -------> 8y = -3x + 23
2. divide each term by the coeffiecient of the y term
------> y = (-3/8)x) + 23/8
try the other two, let me know what you get
The point pairs chosen is (5, 1) and (-3, 4). First of all, the slope must be found out.
The formula for it is: slope = rise/run
slope = (4 - 1)/(-3 -5) = 3/-8 = -3/8
Point slope form: y - 1 = -3 (x - 5)/8
Slope intercept form: y - 1 = -3x/8 + 15/8
y = -3x/8 + 23/8
Standard form: 8y = -3x + 23
Thats all I rlly needed, thx~!