Question

(1-r/3s)^3
Please answer it step by step.
Thank you!​

Answer 1

=(1− r  /  3 s)*(1− r  / 3 s)*(1−  r /  3 s)

=(1+  −1  / 3 rs)( 1  / 9 r²s²+   −2  / 3 rs+1)

=(1)( 1   / 9 r²s²)+(1)( −2  / 3 rs)+(1)(1)+( −1  / 3 rs)( 1  /  9 r²s²)+( −1  / 3 rs)( −2  / 3 rs)+( −1  / 3 rs)(1)

= 1  / 9 r²s²+ −2  / 3 rs+1+ −1  / 27 r3s3+ 2  / 9 r²s²+  −1  / 3 rs

= −1  / 27 r³s³+ 1  / 3 r²s²−rs+1