(3x-y)^5

Question

(3x-y)^5

marigirl · Answer

Are we expanding?

littlebird · Answer

3^5x^5-y^5?

marigirl · Answer

are we expanding using Binomial expansion? can u confirm? 
your answer will START to look like this ...... 243x^5-405x^4y .....

anonymous · Answer

Yeah its an expanding problem

marigirl · Answer

Right best method to use is Binomial expansion (which also uses coefficient from the pascal triangle) ...I will give u a brief explanation but I am happy to explain further if you wish ok?

So first we need to coefficients from the pascals triangle (look at the row with 5 since that is the power we are working with).
We have 1   5   10    10   5   1
Then we deal with the powers and the terms inside the bracket$$1 (3x)^5*(-y)^0 + 5 (3x)^4*(-y)^1 + 10 (3x)^3*(-y)^2+10 (3x)^2*(-y)^3 + 5 (3x)^1*(-y)^4+  (3x)^0*(-y)^5$$

marigirl · Answer

(3x) term will decent and (-y) term will increase in ascend

marigirl · Answer

sorry it looks s messy, it was my first time explaining. Sorry

marigirl · Answer

$$243x^5-405x^4y+270x^3y^2-90x^2y^3+15xy^4-y^5$$