now we are doing exercise 3.1 question number one roman number four exercise three point one question number one roman numeral four roman number four we have x cube minus y cubed minus 1 2 5 z cube minus 15 x y z okay solution x cube minus y cube and 1 2 5 i can write down as 5 z whole cube minus 15 x y z all the questions are same for question number one you are going to use the same formula a q plus b cube the formula will be a minus b whole cube plus
twice a b so x y a plus b so a a minus b so x minus y minus 5 z whole cube minus 15 x y z so a minus b whole cube so x square so a wait wait let me write down x minus y whole cube minus five z whole q three x y plus three x y into this one it will be three wait write down as it is three x y x minus y minus 15 x y z so a cube minus b cube it will be a minus b minus five
z okay and a square a square so x minus y whole square minus this dash of plus a b a b it will be 5 z into x minus y plus b square that is 5 z whole square and next this one take 3 x y common so let me write down here plus 3 x y continuation so x minus y from here taken three x y three five z fifteen so minus five is left okay and x y goes out so z is left so if you take x minus y minus 5 z command
from both you'll get x minus y minus 5 z if you take common then you are going to get x minus y whole square plus five z into x it will be five x z minus five z into y equal you will get five y set plus five z whole square five z whole squared it is 25 z square so and you have taken you have taken sorry you have taken x minus y minus five z so from here you it will what left out is three x y so this is what going to left
out from this one now x minus y minus five z you open the bracket x minus y whole square it will be x square minus twice a b plus b square that is y square 2 x squared minus twice x y plus y square plus 5 x z [Music] minus 5 y z plus 25 z square plus 3 x y now let us write down the final answer x minus y minus 5 z x square i can take y square plus y square plus z square take this one also plus five this is 25 z
square sorry around 25 z square now 2 x y and 3 x y so plus minus 2xy plus 3xy you'll get plus xy and minus 5yz and 5xz so minus 5f y z plus 5 zx so this is what going to ref left out so this is your answer thank you so much we will meet in the next video
