Question

If -2x+ y =6 and -7x-4y=-8 are true equations what would the value of -9x-3y

Answer 1

`-(106)/(5) or -21.2`

Explanation:

First we would have to get x and y-values by solving systems of equations:

isolate one of the variable from any of the first 2 equations given:

-2x+ y =6 would be y = 2x + 6 when y is isolated.

now plug this equation in for the y given in the second equation:

-7x -4(2x + 6) = -8

Now solve to get the x-value,

-7x - 8x - 24 = -8

-15x - 24 = -8

-15x = 16

x =
`-(16)/(15)` or -1.06

To solve for y-value, substitute the gotten x-value in any of the 2 equations and solve:

y = 2(
`-(16)/(15)`) + 6

y =
`(58)/(15)` or 3.86

Now that we have the x and y-values, substitute them in for the 3 equation given:

-9(
`-(16)/(15)`) -3(
`(58)/(15)`)

=>
`-(106)/(5)` or -21.2 = Final Answer

Hope this helps!