Question

5x+4y=73 -4x+4y=-8

Answer 1

what are we doing here?

Answer 2

it should be solving the system of equation

Answer 3

solve 1 equation for y.

let's take -4x + 4y = -8 divide everything by 4 to simplify this equation. what do you get?

Answer 4

idk system of equation stupid apex:/

Answer 5

So ignore my idea and do substitution

Answer 6

wait for it..

Answer 7

so we've taken -4x + 4y = -8

we have mutliples of 4 in this equation that we can use to simplify it before solving for y.

-4x/4 +4y/4 = -8/4

-x + y = -2 solve for y

- x + x + y = +x - 2

y = x - 2

Now we've turned one of our equations to solving for y, we can substitute this into the other equation not used to solve for a variable.

5x + 4y = 73 substitute in the "y" equation

5x + 4( x - 2 ) = 73

5x + 4x - 8 = 73

9x - 8 = 73

9x - 8 + 8 = 73 + 8

9x = 81

x = 9

Now we're going to do the same thing we did with y, but now we're going to input "x" into one of our equations to solve for y.

Answer 8

gauss-jordan elimination is much more easier if you have the time to study it.

Answer 9

And there it is :D

Answer 10

5x+4y=73 -4x+4y=-8 ,so 5x+4y=-8 and 73-4x+4y=-8 ,then 9x-73=0 ,x=73/9 ,let do y, y=(-5/4)(73/9 -8)

Answer 11

what happens when you input "x = 9" into -4x + 4y = -8?

-4(9) + 4y = - 8

-36 + 4y = -8

-36 + 36 + 4y = -8 + 36

4y = 28

y = ?

Answer 12

@chris00 i've heard of it, never used it. :(

Answer 13

its the same thing we're doing here, matrix manipulation to isolate the variables/unknowns

Answer 14

ahh... I hate matrices :|

Answer 15

matrices are awesome

Answer 16

-4x + 4y = -8 isn't correct, -4x+4y=-81

Answer 17

you create an augmented matrix bro.

Answer 18

5x+4y=73 .................. (1)
-4x+4y=-8 ................. (2)
multiply (2) by -1
4x-4y=8 .................. (3)
adding (1) & (3)
9x=81
x=9
substitute in (1) or (2) to get the value of y

Answer 19

I taught the system is
5x+4y=-8
73 -4x+4y=-8