If you mean,

(3x^2)(e^(6x-10x-3)) + (6x)(e^(3x^2-5x^2-3x+6-52))

i.e.

3x^2 e^(6x-10x-3) + 6x e^(3x^2-5x^2-3x+6-52)

(which both say the same whereas your version opens more brackets than it closes - latex would reject it - did it?)