The product of 2x^2+6x-8 and x+3 is:
= (2x^2+6x-8)(x+3)
= 2x^3 + 6x^2 - 8x + 6x^2 + 18x - 24
= 2x^3 + 12x^2 + 10x - 24
This answer can still be simplified by dividing everything by 2
= x^3 + 6x^2 + 5x - 12
So the product of 2x^2+6x-8 and x+3 is equal to x^3 + 6x^2 + 5x - 12.