How do you solve 8x + 40 = 4x?

2 Answers
Jul 15, 2017

See a solution process below:

Explanation:

Step 1) First, subtract color(red)(40) from each side of the equation. This will begin the process of isolate the x term while keeping the equation balanced:

8x + 40 - color(red)(40) = 4x - color(red)(40)

8x + 0 = 4x - 40

8x = 4x - 40

Step 2) Subtract color(red)(4x) from each side of the equation to isolate the x term while keeping the equation balanced:

-color(red)(4x) + 8x = -color(red)(4x) + 4x - 40

(-color(red)(4) + 8)x = 0 - 40

4x = -40

Step 3) Divide each side of the equation by color(red)(4) to solve for x while keeping the equation balanced:

(4x)/color(red)(4) = -40/color(red)(4)

(color(red)(cancel(color(black)(4)))x)/cancel(color(red)(4)) = -10

x = -10

Jul 15, 2017

Isolate the variable (x) on one side (typically the left) and "move" everything else onto the other (typically the right). Then simplify.

Explanation:

When you are solving these types of equations, you want to get the x's on one side of the equation, and everything else on the other. Typically, you want all the x's on the left side, and everything else on the right side.

In this case, we have to "move" the 40 to the right side, and "move" the 4x to the left side.

To do this, we can first subtract 40 from both sides:
8x+40=4x
8x+40-40=4x-40

Now we can simplify this equation.
8x=4x-40

To get the 4x onto the left side, we can subtract 4x from both sides:
8x=4x-40
8x-4x=4x-40-4x

Simplifying:
4x=-40

Now, to get the value of x, we can divide both sides by 4:
\frac{4x}{4}=\frac{-40}{4}
x=-10

So, x is equal to -10.