Answer:
(3x+4)(x+1) =
3x*x + 3x*1 + 4*x + 4*1 =
3x²+3x+4x+4=
3x²+7x+4
see attachment for explanation
for moderators: i'm french, i answer on our homework france, we often attach this scheme to explain, free scheme found on the internet (please do not delete for copy reason)
Explanation: