If tanA=1/7 and tanB=1/3 prove that cos2A=sin4B

Me! i really need to get this right before 9. prove the divisibility of 7^6+7^5-7^4 by 11. use factoring so you get a number times 11. just tell me the number. i need this done asap

Calculate the missing value. round the answer to on decimal place. start with 70, increase it by 21%, and end up with

Sam opened a money-market account that pays 3% simple interest. he started the account with $7,000 and made no further deposits. when he closed the account, he had earned $420 in interest. how long did he keep his account open?