How do you solve the system of equations -3x-4y=203x4y=20 and x-10y=16x10y=16?

2 Answers

x=-4 x=4 and y=-2y=2

Explanation:

Given system of equations

-3x-4y=20\ ........(1)

x-10y=16\ ........(2)

Multiplying (2) by 3 & adding to (1) as follows

-3x-4y+3(x-10y)=20+3\cdot 16

-34y=68

y=-2

setting y=-2 in (1) we get

x=\frac{-4y-20}{3}

=\frac{-4(-2)-20}{3}

=-4

Jul 9, 2018

Express x as a function of y and replace in the second equation.

Explanation:

To get a very fast answer to your problem, just use one of the two equations to express x or y. In this case, let's do it with x.

So, we have the following system:

1) \ -3x-4y=20
2) \ x-10y=16

If we express x in 2), then we have:

x=16+10y

Then we replace x in 1) with what we obtained with 2) and we get:

-3*(16+10y)-4y=20

Then develop the brackets:

-48-30y-4y=20

Solve for y:

-34y=68

y=-2

Then replace y in 2) by what you found:

x-10*(-2)=16

Solve for x:

x=-4

Finished!