Question

For which the value of m, x+3 is the factor of the polynomial x³-2mx+21?. plzz help guys. The answer is. m=1. can somebody do it and show it plzzzz

Answer 1

let
p(x)=x³-2mx+21,

if x+3 is a factor of p(x) then

p(-3)=0,

(-3)³-2m×(-3)+21=0,

-27+6m+21=0,

-6+6m=0,

6m=6,

then

m=1

Answer 2

put X =-3
$( - 3)^{3} - 2m( - 3) + 21 = 0 \\ - 27 + 6m + 21 = 0 \\ m = (27 - 21) \div 6 \\ m = 1$