## Understanding (c + d)^2

The expression (c + d)^2 is a common algebraic expression that represents the square of the sum of two variables, c and d. It is often encountered in various mathematical contexts, especially when dealing with quadratic equations and polynomials.

### Expanding the Expression

To understand the meaning of (c + d)^2, we need to expand it. This means multiplying the expression by itself:

(c + d)^2 = (c + d)(c + d)

Using the distributive property (or FOIL method), we multiply each term in the first set of parentheses by each term in the second set:

(c + d)(c + d) = c(c + d) + d(c + d)

Expanding further:

c(c + d) + d(c + d) = c^2 + cd + dc + d^2

Finally, combining like terms:

c^2 + cd + dc + d^2 = **c^2 + 2cd + d^2**

### Key Points

**The square of a sum is not equal to the sum of the squares:**It's important to remember that (c + d)^2 is**not**equal to c^2 + d^2. The middle term, 2cd, arises from the cross-multiplication of terms in the original expression.**Applications in various fields:**This formula is crucial for understanding quadratic equations, simplifying polynomials, and solving problems in physics, engineering, and other scientific disciplines.

### Example

Let's say c = 3 and d = 4. We can use the formula to calculate (c + d)^2:

(c + d)^2 = (3 + 4)^2 = 7^2 = **49**

Alternatively, we can use the expanded form:

c^2 + 2cd + d^2 = 3^2 + 2(3)(4) + 4^2 = 9 + 24 + 16 = **49**

Both methods lead to the same answer, demonstrating the correctness of the formula.

Understanding (c + d)^2 is fundamental for mastering algebra and applying it to various mathematical and scientific problems. By understanding the expansion and its applications, you can confidently tackle more complex equations and gain a deeper understanding of mathematical concepts.