Question

How would I solve this using the substitution method? 4p=3q
3p-q=15

Answer 1

4p=3q
so p=3q/4
plug this p value in 2nd equation
to get p val

Answer 2

if p=3q/4, dont i already have myp value? what about my q value?

Answer 3

now substitute value of p in 4p=3q

Answer 4

you'll get q

Answer 5

4(3q/4)=3q
12q/4=3q
3q=3q
now what?

Answer 6

dude substitute the value p=3/4*q in the second equation

Answer 7

I think if you rearrange the first equation so q=4p/3 your substitution will be easier. Not more correct, just easier to calculate.

Answer 8

q=60,p= 45

Answer 9

sorry these were with negative sign

Answer 10

substitutions:

in this case, define p as a function of q: p(q)

p(q) = 3q/4

3p(q) - q = 15

Answer 11

p=5.5555555555556, q=4p/3

Answer 12

no no p= -45, q=-60

Answer 13

3(-45) -(-60)=15
-135+60=15
-75=15
So its not p=-45, q=-60

Answer 14

4*-45=3*-60 therefore it is the answer

Answer 15

but not if it doesn't agree with BOTH equations. it only agrees with one of them. doesnt it have to be right on both equations?

Answer 16

of course it should i am also wondering how is it possible

Answer 17

\[4p=3q ~and~ 3p-q=15\]So\[q=\frac{4p}{3}~and~3p-q=3p-\frac{4p}{3}=15 \implies 5p=45 \implies p=9 \implies q=12\]\[\implies (p,q)=(9,12)\]

Answer 18

Don't make the easy ones hard.