(a-1)=3(a+1)

Solution for (a-1)=3(a+1) equation:

Simplifying
(a + -1) = 3(a + 1)

Reorder the terms:
(-1 + a) = 3(a + 1)

Remove parenthesis around (-1 + a)
-1 + a = 3(a + 1)

Reorder the terms:
-1 + a = 3(1 + a)
-1 + a = (1 * 3 + a * 3)
-1 + a = (3 + 3a)

Solving
-1 + a = 3 + 3a

Solving for variable 'a'.

Move all terms containing a to the left, all other terms to the right.

Add '-3a' to each side of the equation.
-1 + a + -3a = 3 + 3a + -3a

Combine like terms: a + -3a = -2a
-1 + -2a = 3 + 3a + -3a

Combine like terms: 3a + -3a = 0
-1 + -2a = 3 + 0
-1 + -2a = 3

Add '1' to each side of the equation.
-1 + 1 + -2a = 3 + 1

Combine like terms: -1 + 1 = 0
0 + -2a = 3 + 1
-2a = 3 + 1

Combine like terms: 3 + 1 = 4
-2a = 4

Divide each side by '-2'.
a = -2

Simplifying
a = -2