1. ## system of eauations

7x=4y=-2
10x-3y=32

i need to use subsitution for this i dont get it? explain?

2. Originally Posted by mcinnes
7x=4y=-2
10x-3y=32

i need to use subsitution for this i dont get it? explain?
You have a typo in your first equation.
Not a real good candidate for substitution, but if you have to.....

Step 1: Solve the first equation for x or y (whichever is easier).

Step 2: Substitute that into your second equation to solve for your 1st variable.

Step 3: Finally, use your answer from Step 2 and substitute into Step 1 to solve for the 2nd variable.

After you fix your typo, I can be more specific.

3. sorry i was in a rush,
here is the equation
7x+4y=-2
10x-3y=32

4. Originally Posted by mcinnes
sorry i was in a rush,
here is the equation
7x+4y=-2
10x-3y=32
Solve the first equation for x or y. Let's choose y for no reason.

$\displaystyle 7x+4y=-2$

$\displaystyle 4y=-7x-2$

$\displaystyle y=-\frac{7}{4}x-\frac{1}{2}$

Now substitute this back into the second equation.

$\displaystyle 10x-3\left(-\frac{7}{4}x-\frac{1}{2}\right)=32$

$\displaystyle 10x+\frac{21}{4}x+\frac{3}{2}=32$

$\displaystyle 40x+21x+6=128$

$\displaystyle 61x=122$

$\displaystyle x=\frac{122}{61}$

$\displaystyle x=2$

Now plug this value into either equation you started with to find y.