if a negative charge particle is placed on the left side and a higher positive charge particle is placed on the right side, why is the location that makes electric field zero is on the left of negative charge rather than in between or on the right of positive charge

Answer 1

E is directed the direction that a + test charge will move. Put it in between, both charges move it to left (E to left). Put it to the left of both, the + test charge will be attracted to the right by the - charge, but to the left by the + charge, and and some point these will add to zero.