Question

Can someone check my SAT questions answers : Point slope question and slope intercept.

Define a line that passes through (-1,4) and (-3,2)
slope 1.
y-4=1(x--1)
y-4=x-1
y=x+3

Define a line that passes through (3,2) and has a slope of 3
y-2=3(x-3)
y-2=3x-9
y=3x+7

Define a line that has a slope of -1 and y intercept of 4
y=mx+b
y=-1x+4

What is the slope of a line defined by y=-12x +89
y=mx+b
-12

Answer 1

there are several methods you can employ, but traditionally we first calculate for the slope
then use the point-slope form to solve for the equation

Answer 2

\[m = \frac{y_2-y_1}{x_2-x_1}\]
\[y-y_1=m(x-x_1)\]
solve for m
then use the second equation to solve for y

Answer 3

show me your solution, so I know where you need help with

Answer 4

i posted in original quesiton now. thanks for your help, can you help me check

Answer 5

are they all right?

Answer 6

y-4=1(x--1)
do that part again

Answer 7

Define a line that passes through (-1,4) and (-3,2)

(2-4)/(-3--1)
Slope = 1

y-y1 = m(x-x1)
y-4 = 1(x--1)
y-4 = x-1
y = x+3

Answer 8

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

Answer 9

negative and negative makes positive

Answer 10

Oh my gosh! Thanks for your help haha. Silly mistakes.

Answer 11

the rest is the same concept

Answer 12

so the rest are correct?

Answer 13

I don't know, that is something you will need to figure out by double checking

Answer 14

y = mx + b
b is the y-intercept right?

Answer 15

yes.

Answer 16

then you did well

Answer 17

next time, you can also just put all in the same equation
\[y-y_1 =\frac{y_2-y_1}{x_2-x_1}(x-x_1)\]

Answer 18

this kind of technique is a good practice for physics

Answer 19

alright thanks ill memorize that!
haha but would it work for a question like

line c passess through (3,6) and the origin and line d is perpendicular to line c. which of the following could be the equation of line d?

ah im working it out atm.
but how do u know which coordinate is x1 or/y1 if its like that word problem above
(0,0), (3,2)
or
(3,2) (0,0)