You can complete the last operations to find the value of ADX indicator in easier way

• Calculate Directional Movement Index (DX). It equals the absolute value of +DI14 minus -DI14 divided by the sum of +DI14 and – DI14. It is also expressed in % terms.

• Calculate Average directional index (ADX). It is the 14 period moving average of DX.

ADX = MA [((+DI) – (-DI)) / ((+DI) + (-DI))] x 100;