Question

4x+5y=-5
3x+y=21 if the system cannot be solved state that it cannot be solved and explain why.. plzz help!!

Answer 1

My recommendation for this one is to turn the second equation around for y, then sub it into the first equation:
4x+5y=-5
3x+y=21--->y=21-3x
^^^sub this expression for y into the first eqn:

4x+5(21-3x)=-5

once you find x, plug in that value into either eqn to find y
...assuming a unique solution exists

Answer 2

hmm how can i do that?

Answer 3

can't solve this for x?

4x+5(21-3x)=-5

Answer 4

hmm do i multiply 5 with 3x?

Answer 5

distribute\[a(b+c)=ab+ac\]

Answer 6

105+15x?

Answer 7

-15

Answer 8

yes

Answer 9

now simplify the whole thing and solve for x

Answer 10

really i was right? lol

Answer 11

yeah, and if distribution is new to you then either you have been skipping school or your teacher sucks

Answer 12

no its not new lol and ive never skip school lol

Answer 13

I'm just messin'
so can you solve for x now?

Answer 14

yea i know and wait let me see if i can do it lol

Answer 15

hmm im kinda stuck

Answer 16

ok i did 4x+105-15x=-5 am i right so far?

Answer 17

yes

Answer 18

ok do i put -105 and put it on the -5 and it will be -110?

Answer 19

yep

Answer 20

no way! lol

Answer 21

yes way :)

Answer 22

so then it will be 11x=-110? am i right i hope so lol

Answer 23

almost, but watch those negative signs

Answer 24

o i mean -11 right?

Answer 25

right, so x=...?

Answer 26

10?

Answer 27

right, now we can use any equation we want to find y

I suggest remembering our earlier expression we wrote down

4x+5y=-5
3x+y=21--->y=21-3x

now that we know x=10, we can find y with the last formula above

Answer 28

so i plug that into all the x's right?

Answer 29

you only need to use one of the equations
pick whichever you prefer

but yes, just sub in x=10 into any of the equations and solve for y

Answer 30

i did it on the y=21-3(10) and i got y=-9 am i right?

Answer 31

yes you are :)

Answer 32

omg so x=10 and y=-9?

Answer 33

let's make sure they are the right answers

our equations were

4x+5y=-5
3x+y=21

if we plug in x=10 and y=-9 both these should be true, or else we messed up

Answer 34

4(10)+5(-9)=?
3(10)-9=?

you should check yourself that these values do in fact satisfy both equations

good job :)

Answer 35

i did it and it came out right=)

Answer 36

hooray, we win
well that covers the three possibilities in systems (none, infinite, or one unique solution), gotta go
see ya, and good luck!

Answer 37

thnx u make me smart lol

Answer 38

impossible, it must have just been sleeping until now :P

Answer 39

no u made me smart lol thnx for explaining