The expression you provided is:
(C² + 2cd - 15d²) / (4c² + 20cd)
To simplify this expression, we can factor the numerator and denominator if possible, and then cancel out any common factors:
Numerator: C² + 2cd - 15d²
The numerator does not appear to be factorable.
Denominator: 4c² + 20cd
We can factor out a common factor of 4 from each term:
4(c² + 5cd)
Now we can simplify the expression by canceling out the common factors:
(C² + 2cd - 15d²) / (4c² + 20cd) = (C² + 2cd - 15d²) / 4(c² + 5cd)
Therefore, the simplified expression is (C² + 2cd - 15d²) / 4(c² + 5cd).