Question

Solve using two different methods. Explain which method you found to be more efficient.
a.) 3x-9y=3
6x-3y=-24

Answer 1

@hba please help me :D

Answer 2

We can use two methods

1-Substitution

2-Elimination.

Answer 3

@dusty Do you know how to do these methods ?

Answer 4

no i don't really. Will you explain it to me?

Answer 5

Sure thing.

lets take an example first.

Answer 6

Elimination method:
When adding two equations, you basically add all parts of them. Say you had the equations:
4x + 5y = 14
-4x - 3y = -10

Adding them would give 2y = 4

4x + 5y = 14
+ -4x - 3y = -10
2y = 4

As you can see, the 4x and -4x cancelled out, therefore eliminating the variable x, leaving an equation with only one variable (y), able to be solved.

2y = 4
y = 2

Now that you have a value for y, you must find one for x. To do this, just substitute the value for y into either original equation, and solve it for x

4x + 5(2) = 14
4x + 10 = 14
4x = 4
x = 1

Your solution for these two equations is (1, 2).

Answer 7

x + y = 4, and 2x + y = 7.

First you work in one equation, solving for one variable in terms of another. Let's solve for y in terms of x in the first equation (you can do whichever variable in whichever equation you want, but you should experiment, and start recognizing which is the simplest one).

x + y = 4
-x -x
y = 4 - x

Now this is where the substitution comes in. We substitute this value for y in the second equation.

2x + y = 7
2x + (4 - x) = 7
2x + 4 - x = 7
Combine like terms...
x + 4 = 7
-4 -4
x = 3

Now you've solved for one variable, x, but you still need y. So...substitute your value for x into either equation and solve that linear equation to find y.

x + y = 4
3 + y = 4
-3 -3
y = 1

The solution to this equation is x = 3, y = 1.

Answer 8

@dusty Source:Tripod


If you want a step by step solution i will solve it for you.

Answer 9

Its okay I think i get it (: thanks alot!!

Answer 10

Your'e welcome.