Question

Solve the simultaneous equations 4x+8y=-4 2y-5x=23

Answer 1

Answer:

x = -4,  y = 3/2

Step-by-step explanation:

simplify the 1st equation by dividing each term by 4 to get:

x + 2y = -1

-5x + 2y = 23

Subtract to get: 6x = -24

x = -4

find 'y':    2y - 5(-4) = 23

               2y + 20 = 23

               2y = 3

                y = 3/2

Answer 2

Answer:

y is equal to 1.5, and x is equal to -4

Step-by-step explanation:

given:

$4x + 8y = -4$

$2y - 5x = 23$

We can start by factoring 4 out of the first equation:

$x + 2y = -1$

Now let's multiply it by -5:

$-5x - 10y = 5$

We'll rearrange the other equation to match that (just for clarity):

$-5x + 2y = 23$

Now let's subtract the modified equation from that:

$\begin{array}{c}-5x + 2y = 23\\-5x - 10y = 5\\ \ \ \ \ \ \ \ \ \ \ 12y = 18\end{array}$

So y is equal to 18/12, or 1.5

Let's plug that into one of the first equations and see what we get:

$2y - 5x = 23\\2(1.5) - 5x = 23\\3 - 5x = 23\\-5x = 20\\x = -4$

Giving us an x value of negative four.  Let's plug that into the other equation to confirm:

$4x + 8y = -4\\4(-4) + 8y = -4\\-16 + 8y = -4\\-4 + 2y = -1\\2y = 3\\y = 1.5$

That matches up, so our answer is correct.