Answer:
The correct option is C.
Explanation:
If a function f(x) is completely divisible by (x-a), it means (x-a) is a factor of f(x) and x=a is a root of that polynomial.
The given polynomial is
![P(x)=2x^2+9x-5](https://img.qammunity.org/2020/formulas/mathematics/middle-school/5ydjo6lpxjucwwyxgtrqbwd8dzmu5p3i0t.png)
It is given that when David divide the above polynomial by (2x-1), then he get
![Quotient=x+5](https://img.qammunity.org/2020/formulas/mathematics/middle-school/6tilgm8u10m446lve92cpuon6gsif5pahq.png)
![Remainder=0](https://img.qammunity.org/2020/formulas/mathematics/middle-school/ykt4ie1xyeaso5oy400mev3fydoco5c9a5.png)
Since the remainder is zero it means P(x) is completely divisible by (2x-1) or (2x-1) is a factor of P(x).
![2x-1=0](https://img.qammunity.org/2020/formulas/mathematics/high-school/7ptirg3z4vkbz5et2d54nifwebv991bud5.png)
Add 1 on both the sides.
![2x=1](https://img.qammunity.org/2020/formulas/mathematics/middle-school/ntmdys39zldczb22g4vs9lngx5cyj5wx3b.png)
Divide both sides by 2.
![x=(1)/(2)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/87qtte8lpqsqdotr3yo8hz906fxgd53q7j.png)
It means
must be a root of the polynomial
.
Therefore, the correct option is C.