a) \(\left(7^5+7^9\right)\left(5^4+5^6\right)\left(3^3.3-9^2\right)=\left(7^5+7^9\right)\left(5^4+5^6\right)\left[3^4-\left(3^2\right)^2\right]=\left(7^5+7^9\right)\left(5^4+5^6\right)\left(3^4-3^4\right)=\left(7^5+7^9\right)\left(5^4+5^6\right).0=0\)