Solve by completing the square x^2+2x-3=0

What is the binomial expansion of (2x-3)^5

Ineed me i stuck and i don’t want to get it wrong

As voters exit the polls, you ask a representative random sample of voters if they voted for a proposition. if the true percentage of voters who vote for the proposition is 63%, what is the probability that, in your sample, exactly 5 do not voted for the proposition before 2 voted for the proposition? the probability is