How do you solve -2(x-4)=2?

1 Answer
Jan 11, 2016

x=-3

Explanation:

Given: -2(x-4)=2
color(magenta)("~~~~~~~~~~ Short Cut Method ~~~~~~~~~~")
Jumping steps by doing some of it in my head!

-2x-8=2
2x=6
x=3

color(magenta)("~~~~~~First Principle Method With Extensive explanation~~~~~~~~~~")

I am choosing to rewrite it like this:

-1xx2xx(x-2)=2 ...........................Equation (1)
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
color(blue)("Consider just the "2xx(x-4)

This is the same as 2 of (x-4)

Which is color(green)((x-4)+(x-4)->)color(magenta)( x+x-4-4)

So 2(x-4)-> 2x-8
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Putting this back into Equation (1) gives:

-1xx(2x-8)=2

color(brown)("Multiplying the bracket by -1 changes the sign of everything inside the bracket")

color(brown)(-2x+8=2)
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
color(blue)("'Getting rid' of the 8 on the left hand side")

Subtract color(blue)(8) from both sides.

color(brown)(-2x+8 color(blue)(-8)=2color(blue)(-8))

-2x+0=-6

Multiply both sides by -1 changing all the signs

2x=6
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
color(blue)("'Getting rid' of the 2 in "2x)

Divide both sides by 2. This is the same as color(blue)(xx1/2)

color(brown)(2x color(blue)(xx1/2)=-6color(blue)(xx1/2))

2/2 x = -6/2

But 2/2 = 1 giving:

x=-3