Question

show that y -1 is a factor of y power 20 -1 and y power 21 -1​

Answer 1

$p(y)=y^(20)-1$

and $\\g(y)=y^(21)-1$

y-1=0

y=1

by factor theorem

$p(1)=1^(20)-1 \\p(1)=1-1\\p(1)=0$\

and

$g(1)=1^(21)-1\\g(1)=1-1\\g(1)=0$\

hence proved