400=a(0-1000)(0-1500)(0-1500)(0-2000)

Solution for 400=a(0-1000)(0-1500)(0-1500)(0-2000) equation:

Simplifying
400 = a(0 + -1000)(0 + -1500)(0 + -1500)(0 + -2000)

Combine like terms: 0 + -1000 = -1000
400 = a(-1000)(0 + -1500)(0 + -1500)(0 + -2000)

Combine like terms: 0 + -1500 = -1500
400 = a * -1000(-1500)(0 + -1500)(0 + -2000)

Combine like terms: 0 + -1500 = -1500
400 = a * -1000 * -1500(-1500)(0 + -2000)

Combine like terms: 0 + -2000 = -2000
400 = a * -1000 * -1500 * -1500(-2000)

Reorder the terms for easier multiplication:
400 = -1000 * -1500 * -1500 * -2000a

Multiply -1000 * -1500
400 = 1500000 * -1500 * -2000a

Multiply 1500000 * -1500
400 = -2250000000 * -2000a

Multiply -2250000000 * -2000
400 = 4500000000000a

Solving
400 = 4500000000000a

Solving for variable 'a'.

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

Add '-4500000000000a' to each side of the equation.
400 + -4500000000000a = 4500000000000a + -4500000000000a

Combine like terms: 4500000000000a + -4500000000000a = 0
400 + -4500000000000a = 0

Add '-400' to each side of the equation.
400 + -400 + -4500000000000a = 0 + -400

Combine like terms: 400 + -400 = 0
0 + -4500000000000a = 0 + -400
-4500000000000a = 0 + -400

Combine like terms: 0 + -400 = -400
-4500000000000a = -400

Divide each side by '-4500000000000'.
a = 0.00000000008888888889

Simplifying
a = 0.00000000008888888889