Question

What is the slope-intercept form equation of the line that passes through (5, 7) and (8, 22)?

y = −5x + 18

y = 5x − 18

y = −5x − 18

y = 5x + 18

Answer 1

y = mx + c is slpoe intercept form... yeah?

Answer 2

how would i go about finding that @Jack1

Answer 3

(5, 7) and (8, 22) are your points on the line, so lets call them
(x1, y1) and (x2,y2)

Answer 4

ok

Answer 5

gradient (m) = rise / run = (y2 - y1)/(x2-x1)
so sub in those values and tell me what you get

Answer 6

@aleisha96

Answer 7

is it 22-7/8-5?

Answer 8

perfect, so that = 15/3
= 5/1
= 5
so m = 5

Answer 9

so now u know the answer cant be a or c, as their gradient is -5, and ours is 5
so must be b or d

Answer 10

so how would we go about finding x and c?

Answer 11

x is a variable, so is y
but c and m are fixed
y = mx + c
y = 5x + c
now take one of the points,
lets use (5, 7)
(x, y)

so sub those values for x and y into the below equation, and solve for c
y = 5x + c

Answer 12

isnt slope intercept formula y=mx+b

Answer 13

ok, same thing though
y = 5x + b
sub in and solve for b

Answer 14

so its 5x+ ????

Answer 15

yeah... its
y = 5x + b and a point on that line is (5,7)
this point is an x,y coordinate
so sub the x value of 5 into the above exuationm and sub the y value of 7 into the smae equation, and what are you left with>

Answer 16

5x+7?

Answer 17

no
y = 5x + b
sub in the y value
7 = 5x + b
now sub in the x value
7 = 5(5) + b

Answer 18

so expand it out and leave the b on one side of the equals sign alone
7 = 5(5) + b
7 = 25 + b
therefore b = ...?

Answer 19

-18

Answer 20

perfect,

Answer 21

so its b!

Answer 22

yep! ;D

Answer 23

can you help me with another question

Answer 24

of course, shoot

Answer 25

Given that f(x) = 2x + 5 and g(x) = x − 7, solve for f(g(x)) when x = −3.

−15

−8

10

25

Answer 26

f(x) = 2x + 5 and g(x) = x − 7, solve for f(g(x)) when x = −3.
a simple way to look at this is
g(x) = x − 7... lets call g(x) "p" instead
p = x − 7

now
f(x) = 2x + 5, and when f(p)

Answer 27

ok

Answer 28

f(x) = 2x + 5
f(p) = 2p + 5 ... and remember p = x − 7, so

f(p) = 2(x − 7) + 5
f(p) = 2x − 14 + 5
f(p) = 2x − 9

now the final part is f(g(x)) when x = −3
f(p) = 2x − 9

Answer 29

now the final part is f(g(x)) when x = −3
f(p) = 2(-3) − 9
f(p) = -6 − 9
f(p) = -15

so f(g(x)) at f(g(-3)) is -15

Answer 30

does that make sense?

Answer 31

yes

Answer 32

sweet. nite

Answer 33

@jack 1 thanks