Question

If $p\left(x\right)=4+3x-x^2+5x^3$ then, find $p(-1)$.

Answer 1

Finding the value of $p(-1)$, when $p\left(x\right)=4+3x-x^2+5x^3$:

Values of Polynomial: The value of a polynomial $p\left(x\right)atx=a$ is obtained by putting $x=a$ in the given polynomial. This is denoted by $p\left(a\right)$.

Given equation, $p\left(x\right)=4+3x-x^2+5x^3$
Putting the value $x=-1$ in the given equation, we get,

$$\begin{gathered} \Rightarrow p(-1)=4+3(-1)-{(-1)}^2+5{(-1)}^3 \\ \Rightarrow p(-1)=4+3(-1)-\left(1\right)+5(-1) \\ \Rightarrow p(-1)=4-3-1-5 \\ \Rightarrow p(-1)=4-4-5 \\ \Rightarrow p(-1)=0-5 \\ \Rightarrow p(-1)=-5 \end{gathered}$$

Hence, the value of the given equation at $p(-1)=-5$.