Question

solve this system of linear equations
9x-19y=74
3x+3y=6

Answer 1

You could use the elimination method...multiply that bottom equation by 3...

9x - 19y = 74
3(3x + 3y = 6)

Now you'll have

9x - 19y = 74
9x + 9y = 18

Now subtract your 2 equations....

9x - 19y = 74
-(9x + 9y = 18)

Now you see that 9x - 9x = 0...so you only have the 'y' variable to solve for...

9x - 9x = 0
-19y - 9y = -28y
74 - 18 = 56

So now we have


-28y = 56

Divide both sides by -28....what does 'y' equal??

Answer 2

2

Answer 3

Almost....is it 2 or is it -2 ??

56 / -28 = ...?

Answer 4

-2

Answer 5

is x 0

Answer 6

Right...so now that we know what 'y' equals...take that -2...and substitute it in for the 'y' value in either of your original equations.

lets do...

9x - 19y = 74

now replace 'y' with -2

9x - 19(-2) = 74

Simplify a bit...

9x + 38 = 74

Subtract 38 from both sides of the equation

9x = 36

Divide both sides by 9....x = ?

Answer 7

So yes you'll see that x = 4....and we found that y = -2

Now lets test it....

9x-19y=74
9(4) - 19(-2) = 74
36 + 38 = 74
74 = 74

so this one is correct....now lets check the other...

3x+3y=6
3(4) + 3(-2) = 6
12 - 6 = 6
6 = 6

They are both correct...so you have the correct answers