B^3-5b^2-4b+20 _____________ =0 b^2-25

Question

B^3-5b^2-4b+20
_____________ =0
b^2-25

Answer 1

1) b^3 - 5b^2 - 4b + 20 = b^2( b - 5 ) - 4( b - 5 ) = ( b - 5 )( b^2 - 4 ) = ( b - 5 )( b - 2 )( b + 2 )
2) b^2 - 25 = ( b - 5 )( b + 5 )
3) [( b - 5)( b - 2)( b + 2 ) ] / [( b - 5)( b + 5 ) ] = 0
[( b -2)( b + 2 )] /( b + 5 ) = 0
Ответ 2 ; - 2