Question

can someone help me with solving linear equations with substitution...please?!

Answer 1

sure

Answer 2

cool thanks...\[3x-2y=-3 \] \[x+5y=-18\]

Answer 3

what do you believe it means to "substitute"?

Answer 4

do I have to rewrite one of them?

Answer 5

amistre can help :D:D

Answer 6

I have to fine the value for y or x and substitute it in the equation

Answer 7

not quite a value, more like a suitable "value" so that either the y or x speaks the same language ...

Answer 8

ok so looking at the x+5y=-18 if I "flop" the x to get the 5y to = the rest of the equation...is that the right idea?

Answer 9

you usually try to pick one of the equations and solve for a variable that looks easiest to do ... and if i read you right, yes

x + 5y = -18 ; lets solve for "x"

x = -5y -18 is a suitable value to plug into the other equation

Answer 10

so it can be wither the x or y?

Answer 11

3x -2y = -3 ; but we know that x has to equal some value that is akin to -5y-18 so lets substitute that "value" and solve for y

Answer 12

it can be whatever variable you are most comfortable with solving for

Answer 13

and now I plug it into the the first equation for x...?

Answer 14

yes

Answer 15

3x - 2y = -3

3(-5y-18) -2y = -3 , we have "substituted" and can solve for "y" now

Answer 16

ok Im working it...ty!

Answer 17

youre welcome ; if you get stuck, just let us know :)

Answer 18

y=3

Answer 19

it might .... lets see

3(-5y-18) -2y = -3

-15y -46 -2y = -3

-15y -2y = 43

y(-15-2) = 43

y = 43/-17 ... did i do it right?

Answer 20

i tend to perfer elimination over substitution; less work involved:

3x −2y=−3
x +5y=−18 ; *-3


3x −2y=−3
-3x-15y =54
------------
y(-17) = 51

y = -51/17


2
17
3
----
51

y = -3 is it

Answer 21

i had forgotten how to multiply 3 and -17 lol

Answer 22

I got y=-3, great! Thanks again! I just wasn't sure which one to flop I thought it was always the y! I forget signs all the time...

Answer 23

..... oy vey, your gonna have to just correct my typos

Answer 24

and with elimination I would of just found a number that would of canceled something out between the two...correct?

Answer 25

yep; elimination is "eliminating" a variable by modifying the equations thru a suitable scalar multiple

Answer 26

and if the problem said use 'addition"?

Answer 27

thats the same as elimination; they like to throw different terms at you that amount to the same thing

Answer 28

by adding the equations toghter you eliminate one of the variables after youve scaled one of them

Answer 29

such as \[2x-3y=14\] and\[4x-6y=28\] I could use -2 on the top one?

Answer 30

-2 would work great for the top; or even -1/2 on the bottom

Answer 31

yeah im not fond of fractions...lol

Answer 32

if you simply multiply the top by 2 you will see that the equations are the same

Answer 33

so addition does mean elimination...? I appreciate your help!

Answer 34

addition is another name for elimination yes

Answer 35

ok cool got it. thanks again!