What are the possible values of x in 6x^2 + 432 = 0?

Need this asap if anyone can i would be very grateful. if you could show workings that would really

Find the greatest common factor of the followig monomials 21u^5v,3u^4v^6, and 3u^2v^5

Avery’s piggy bank has 300 nickels, 450 pennies, and 150 dimes. she randomly picks three coins. each time she picks a coin, she makes a note of it and puts it back into the piggy bank before picking the next coin.