plz!!!! help i really need it!!!?

Question

solving a linear system by substitution



1.)

m+2n=1
5m+3n=-23




2.)

x-y=-5
x+4=16


i really appreciate your help!!

Answer 1

take one equation and solve it for that variable.

For example, in the first one solve for m.

m + 2n = 1

subtract 2n from both sides

m + 2n - 2n = 1 - 2n

m = 1 - 2n

Now take the above and put it in the second equation

5 (1 - 2n) + 3n = -23

5 - 10n + 3n = -23

5 - 7n = -23

Subtract 5 from both sides

5 - 7n -5 = -23 - 5

-7n = -28

Divide by -7 on both sides

-7n/-7 = -28/-7

n = 4

m = 1 - 2n

since n = 4, but 4 into the above equation and m = -7

m = -7; n = 4

Second question

x -y = -5
x+4 = 16

The second equation is much easier to solve since it only has one variable.

x + 4 = 16; Subtract 4 from both sides
x + 4 -4 = 16 -4

x = 12

x - y = -5
12 - y = -5 ; Subtract 12 from both sides

12 - y - 12 = -5 - 12
-y = -17

Multiply both sides by -1

y = 17

x = 12, y = 17

Answer 2

1) I can't rember how to do its been awhile since ive taken any math classes.

2) I think you would solve it as follows x+4=16 subtrack 4 from both sides. You get x=12. Then subsitute 12 for x in the first half. So it would be 12 - y = -5. Subtract 12 from both sides -y=-15 so y = 15. Hope that helps

Answer 3

substitution technique necessitates that the equation is expressible in terms of one variable with a coefficient of one

so....
for 1) cancel the "2n" to get
m = 1 - 2n
I would suggest that you put the expression in parentheses to help visualize the substitution into the other equation

5(1 -2n) + 3n = -23
multiply out, simplify and solve for "n"
substitute the found value for "n" into either equation to get the value for "m"

for 2) either variable will work in the first equation

either x = y - 5 OR y = x + 5

but notice the second equation
x = 12
substitute the value into the first equation to get the value for "y"

Answer 4

My teen said that you haven't given enough information. Such as: "Are you solving for x or y?"

Answer 5

basic algebra is the simplest thing on earth. its just like playing with ur imagination. and why don't u refer to ur textbook?

Answer 6

Ask your teacher tomorrow. Don't ask someone else to do it for you.