Calculate (7+8)² : Square of Sum Expression

To solve this problem, we'll use the formula for the square of a sum.

• Step 1: Identify our variables as $a = 7$ and $b = 8$.
• Step 2: Apply the formula $(a + b)^2 = a^2 + 2ab + b^2$.
• Step 3: Substitute into the formula:
  $(7 + 8)^2 = 7^2 + 2 \times 7 \times 8 + 8^2$.
• Step 4: Express the final expression in the most informative form.

Therefore, the expanded expression for $(7 + 8)^2$ is $7^2 + 2 \times 7 \times 8 + 8^2$.

Regarding the choices provided, the correct one is Option 3: $7^2 + 2 \times 7 \times 8 + 8^2$.