How do you work our 3x=4-Y Please help .. if you could explain it in quite a simple way, thanks.

Asked on by lilym

sciencesolve | Teacher | (Level 3) Educator Emeritus

Posted on

You need to isolate the variable y to one side, hence, you need to subtract 4 both sides, such that:

`3x - 4 = 4 - 4 - y => 3x - 4 = -y`

You need to multiply by -1 both sides, such that:

`y = 4 - 3x`

Hence, the equation of the function `y = f(x)` is `y = -3x + 4` .

Since the leading coefficient negative, a = -3, the graph of the function is a line that descends from quadrant 2 to quadrant 4.

The graph intercepts `x` axis at `y = 0` , such that:

-3x + 4 = 0 => -3x = -4 => x = 4/3

The graph intercepts y axis at x = 0, such that:

f(0) = y = 4

Hence, the graph intercepts x and y axis at the points `(4/3,0)` and `(0,4)` and it extends from quadrant 2 to quadrant 4.

namratamadan | Student | (Level 1) eNoter

Posted on

to find out the values of the variables in a linear equation in 2 variables, you need two equations.

in simpler words, since in the your question, the values of both x and y are unknown, u will need two equations to solve it.

as an example, take the following equations:

x+2y=5; and

x-2y= -8

to solve this, add both the equations,

u get:

x+2y+x-2y=5-8

2x= -3

therefore, x= -3/2

then substitute this value of x in anyone of the equations.Lets take the first equation,

x+2y=5

-3/2 +2y=5

2y=5+ 3/2

2y=(10+3)/2

2y=13/2

y=13/4

hence, x= -3/2 and y=13/4

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