CLASS XII PHYSICS ELECTRIC CHARGES AND FIELD DETAILED HANDWRITTEN DERIVATION OF ELECTRIC FIELD DUE TO DIPOLE ON IT'S AXIAL POINT

Here:-

E=epsilon 

K=1/4πE

Dipole moment =P=q×2l

(A-B)²-(A+B)²=4AB

A²-B²=(A+B)(A-B)