Answer:
![f(x)=(1)/(4)x^2](https://img.qammunity.org/2021/formulas/mathematics/college/85hhojsrxu6is966bq0ifu9604i1xb63o2.png)
Explanation:
Recall the vertex form of a quadratic equation:
![f(x)=a(x-h)^2+k](https://img.qammunity.org/2021/formulas/mathematics/high-school/je302k7g40ad9xjfzy7phx2u58uar93mdu.png)
Where (h,k) is the vertex.
We are told that the vertex is (0,0). Therefore:
![f(x)=a(x-0)^2+(0)](https://img.qammunity.org/2021/formulas/mathematics/college/4b9l3qjxfa10ixg84t163z0zf8r60tss3x.png)
Simplify:
![f(x)=ax^2](https://img.qammunity.org/2021/formulas/mathematics/college/19yf7ljshj0lsy6dtei7ku4itek4gffyll.png)
So, to finish the equation, we need to find a.
We know that a point is (2,1). Thus, substitute 1 for f(x) and 2 for x:
![1=a(2)^2](https://img.qammunity.org/2021/formulas/mathematics/college/lgn6dpqvg8r6djvtmzifwrvpmiutkfh39y.png)
Square:
![1=4a](https://img.qammunity.org/2021/formulas/mathematics/college/pv0sr0zyie72umeoq27edqohpdyjh87fc5.png)
Divide both sides by 4:
![a=(1)/(4)](https://img.qammunity.org/2021/formulas/mathematics/college/2cblplohze7u9yeuiy1rx4ap4arkl3ayxi.png)
So, our a value is 1/4.
And we can thus complete our equation:
![f(x)=(1)/(4)x^2](https://img.qammunity.org/2021/formulas/mathematics/college/85hhojsrxu6is966bq0ifu9604i1xb63o2.png)
And we are done :)