I don't know what factor symbolically means but...
2x² + 11x + 15
First, find what two numbers when multiplied together make 30 (this comes from the first and and last term multiplied together; 2 * 15) but add up to make 11 (the middle term). Your numbers are 5 and 6.
2x² + 6x + 5x + 15
Now factor by grouping:
2x(x + 3) + 5(x + 3)
Your factors are (2x + 5)(x + 3)
