(15p⁺⁴.q⁻⁶) /(-20p⁻¹².q⁻³).
Remember that a⁻ⁿ = 1/aⁿ and 1/a⁻ⁿ = aⁿ
(-15/4).(p⁻⁴.q⁻⁶)(p⁺¹².q⁺³).
(-15/20).(p⁻⁴.p¹².q⁻⁶.q³)
Remember aⁿ.aˣ = aⁿ⁺ˣ
(-15/20).(p⁸.q⁻³)
-3/5(p⁸.q⁻³)
Just choose any combination so that a is negative and b is positive, and vice versa. For example, if a = 3 and b = -6, |3-6| ≠ |3| + |-6|.
This is because |-3| = 3, and |3|+|-6| = 3+6 = 9.
3≠9.