# Math Help - Please find the 4th term in expansion

1. ## Please find the 4th term in expansion

nb

2. Originally Posted by oceanmd
$(x^2-y)^6$

${6\choose3}(x^2)^3(-y)^0=20x^6$

Wil you please check the solution and correct if it is wrong.

Thank you
why is the power of -y zero?

3. Originally Posted by oceanmd
${6\choose3}(x^2)^3(-y)^3=20x^6(-y)^3$

Is it correct now?

Thanks
yes, using of course, $(a + b)^n = \sum_{k = 0}^n {n \choose k}a^kb^{n - k}$

write it as $-20x^6y^3$