Question

if ( x+1 ) is the factor of x³- ax²+ 5x find the value of a​

Answer 1

Answer:

⇒  (x−a) is factor of x3−ax2+2x+a−1

⇒  Then, a is the zero of polynomial p(x)=x3−ax2+2x+a−1

⇒  p(x)=x3−ax2+2x+a−1

⇒  p(a)=(a)3−a(a)2+2(a)+a−1

⇒  0=a3−a3+2a+a−1

⇒  a3−a3+2a+a−1=0

⇒  3a−1=0

⇒  3a=1

∴   a=31

Answer 2

$= {x}^{3} - a {x}^{2} + 5x$

$x + 1 = 0 \\ x = - 1$

$= {( - 1)}^{3} - a( { - 1)}^{2} + 5( - 1)$

$= - 1 - a - 5$

$= - 6 - a$

$- a = - 6$

$a = 6$