Question

If 2 is a zero of the polynomial $p\left(x\right)=a{x}^2-5x+b$. What is the value of $12+3b$?

• A. 10
• B. 40
• C. 30
• D. 60

Answer 1

The correct option is C 30

$\because$ 2 is a zero of $p\left(x\right)$; $p\left(2\right)=0$.
$\Rightarrow$ $p\left(2\right)=a\left(2^2\right)-5\left(2\right)+b=0$
$\Rightarrow$ $4\left(a\right)+b=10$ ......... (i)

Multiplying eq(i) with 3, we get
3 $\times$ eq (i)
$\Rightarrow$ $12a+3b=30$