Question

Task 1 Each one is a different problem!?
Solve using two different methods! Explain which method you found to be more efficient?


a.3x-9y=3
6x-3y=--24


b. 7x-3y=20
5x+3y=16


c. y=1/2x-6
2x+6y=19

Answer 1

(a) elimination :
3x - 9y = 3 ---->(-2)
6x - 3y = -24
--------------
-6x + 18y = -6 (result of multiplying by -2)
6x - 3y = -24
-------------add
15y = - 30
y = - 2
sub in -2 for y
3x - 9y = 3
3x - 9(-2) = 3
3x + 18 = 3
3x = -18 + 3
3x = - 15
x = - 5

substitution
3x - 9y = 3
3x = 9y + 3
x = 9/3y + 3/3
x = 3y + 1
now sub 3y + 1 in for x
6x - 3y = -24
6(3y + 1) - 3y = -24
18y + 6 - 3y = -24
18y - 3y = -24 - 6
15y = -30
y = -2
now sub -2 in for y
3x - 9y = 3
3x - 9(-2) = 3
3x + 18 = 3
3x = 3 - 18
3x = -15
x = -5

I believe substitution is more efficient in this problem because when you isolate the variable, there is no fractions involved. Therefore, I find it easier to do.

I am not going to do anymore of these....I think I left you a good example to go by.
Good - luck

Answer 2

@texaschic101
It looks like elimination is more efficient because it took fewer steps to solve the system of equations.

Answer 3

that might be because I included EVERY step. Some steps you could probably combine, making fewer steps.