Solve: 5 + 4(2 - 1)².

To solve the expression 5 + 4(2 - 1)², follow the order of operations, often remembered as PEMDAS (Parentheses, Exponents, Multiplication and Division (from left to right), Addition and Subtraction (from left to right)).

First, address the parentheses:

1. Calculate the expression inside the parentheses: 2 - 1 = 1.

Next, move on to the exponent:

2. Now, evaluate the square: (1)² = 1.

Then, proceed to multiplication:

3. Multiply this result by 4: 4 × 1 = 4.

Finally, perform the addition:

4. Add this product to 5: 5 + 4 = 9.

Thus, the value of the expression 5 + 4(2 - 1)² is 9, making this the correct answer. This demonstrates a solid understanding of the order of operations and how to properly evaluate expressions step by step.