multiply \left(7x^{2}-6x+5\right)\left(4x^{2}+6x-3\right) the simplify
28x^4 + 42x^3 - 21x^2 - 24x^3 - 36x^2 + 18x + 20x^2 + 30x - 15
Combine like terms:
28x^4 + (42x^3 - 24x^3) + (-21x^2 - 36x^2 + 20x^2) + (18x + 30x) - 15
28x^4 + 18x^3 - 37x^2 + 48x - 15
Therefore, the simplified expression is: \boxed{28x^4 + 18x^3 - 37x^2 + 48x - 15}