Question

What is the fourth term in the binomial expansion of (2x – y) 7?

Answer 1

Answer:

$(7C4) (2x)^4 (-y)^{7-4}$

And replacing we got:

$35 (2^4) x^4 (-y)^{-3}$

And then the final term would be:

$-560 x^4 y^3$

Step-by-step explanation:

For this case we have the following expression:

$(2x-y)^7$

And we can use the binomial theorem given by:

$(x+y)^n =\sum_{k=0}^n (nCk) x^k y^{n-k}$

And for this case we want to find the fourth term and using the formula we have:

$(7C4) (2x)^4 (-y)^{7-4}$

And replacing we got:

$35 (2^4) x^4 (-y)^{-3}$

And then the final term would be:

$-560 x^4 y^3$