If you want to find the solutions for the equation:

You first need to click on 'Solve' tab, type in the equation and click on the 'Solve' button:

Click here to see the step by step solution:

So the number of unique solutions is 1.

If you want to calculate the discriminant for the equation:

4r^2 - 28r = -49

4r^2 - 28r + 49 = 0

Discriminant of a quadratic equation ax^2 + bx + c = 0 is calculated by the formula: 

D = b^2 – 4ac 

In our case: a = 4, b = -28, c = 49

Plug into the formula D = b^2 – 4ac:

D = 28^2 – 4*4*49 

D = 0 

click here to see the step by step calculation

D = 0 means there is one real zero of multiplicity 2.