Ques 8:
The Volume(V) in cubic feet of an aquarium id modeled by the polynomial function V(x)= ![x^{3}+2x^{2}-13x+10](https://tex.z-dn.net/?f=%20x%5E%7B3%7D%2B2x%5E%7B2%7D-13x%2B10%20)
a) We have to explain that why x =4 is not a possible rational zero.
By Factor theorem, which states that a polynomial f(x) has a factor (x - k) if and only if f(k)=0.
For this , we will substitute the value of x in the given function.
![V(x)=x^{3}+2x^{2}-13x+10](https://tex.z-dn.net/?f=%20V%28x%29%3Dx%5E%7B3%7D%2B2x%5E%7B2%7D-13x%2B10%20)
![V(4)=4^{3}+2(4)^{2}-13(4)+10](https://tex.z-dn.net/?f=%20V%284%29%3D4%5E%7B3%7D%2B2%284%29%5E%7B2%7D-13%284%29%2B10%20)
![V(4)=4^{3}+2(4)^{2}-13(4)+10](https://tex.z-dn.net/?f=%20V%284%29%3D4%5E%7B3%7D%2B2%284%29%5E%7B2%7D-13%284%29%2B10%20)
which is not equal to zero.
Therefore, x=4 is not a possible rational zero.
(b) To show that (x-1) is a factor of V(x).
By Factor theorem, which states that a polynomial f(x) has a factor (x - k) if and only if f(k)=0.
Let (x-1)=0
So, x=1.
Substituting x=1 in the given function.
![V(1)=1^{3}+2(1)^{2}-13(1)+10](https://tex.z-dn.net/?f=%20V%281%29%3D1%5E%7B3%7D%2B2%281%29%5E%7B2%7D-13%281%29%2B10%20)
![V(1)= -10+10](https://tex.z-dn.net/?f=%20V%281%29%3D%20-10%2B10%20)
V(1) = 0
Therefore, (x-1) is a factor of V(x).
Now we will factorize the given function.
Dividing the given function by (x-1).
On dividing, we get quotient as ![x^{2}+3x-10](https://tex.z-dn.net/?f=%20x%5E%7B2%7D%2B3x-10%20)
So, factored form is = ![(x-1)(x^{2}+3x-10)](https://tex.z-dn.net/?f=%20%28x-1%29%28x%5E%7B2%7D%2B3x-10%29%20)
= ![(x-1)(x^{2}+5x-2x-10)](https://tex.z-dn.net/?f=%20%28x-1%29%28x%5E%7B2%7D%2B5x-2x-10%29%20)
= ![(x-1)(x(x+5)-2(x+5))](https://tex.z-dn.net/?f=%20%28x-1%29%28x%28x%2B5%29-2%28x%2B5%29%29%20)
=![(x-1)(x+5)(x-2)](https://tex.z-dn.net/?f=%20%28x-1%29%28x%2B5%29%28x-2%29%20)
(c) So, the dimensions are 1,2 and -5.