Question

If one zero of x²- (a + 1)x + 6 is 3 then a is
(A) - 4
(B) 5
(C) - 5
(D) 4​

Answer 1

Answer:

The correct answer is option (D) .

Step-by-step explanation:

• Concept : If $\alpha$ is a zero of a polynomial $P(x)$, then $P(\alpha)=0$

Here given $3$ is a zero of polynomial $P(x)=x^2-(a+1)x+6$

          $\Rightarrow P(3)=0\\\Rightarrow 3^2-(a+1)3+6=0\\\Rightarrow 9-3a-3+6=0\\\Rightarrow 12-3a=0\\\Rightarrow 3a=12\\\Rightarrow a=\frac{12}{3}=4$