Let's analyze and verify the problem.

The task is to check whether all four expressions evaluate to $-\frac{1}{2}$.

Expressions:

1. $-\frac{1}{4} + \left(-\frac{1}{4}\right)$
2. $\frac{1}{2} - 1$
3. $-2 \cdot \frac{1}{4}$
4. $-1 + 2$

Evaluation:

1. $-\frac{1}{4} + \left(-\frac{1}{4}\right)$

$-\frac{1}{4} + \left(-\frac{1}{4}\right) = -\frac{1}{4} - \frac{1}{4} = -\frac{2}{4} = -\frac{1}{2}$ This equals $-\frac{1}{2}$.

2. $\frac{1}{2} - 1$

$\frac{1}{2} - 1 = \frac{1}{2} - \frac{2}{2} = -\frac{1}{2}$ This equals $-\frac{1}{2}$.

3. $-2 \cdot \frac{1}{4}$

$-2 \cdot \frac{1}{4} = -\frac{2}{4} = -\frac{1}{2}$ This equals $-\frac{1}{2}$.

4. $-1 + 2$

$-1 + 2 = 1$ This does not equal $-\frac{1}{2}$.

Conclusion:

The fourth expression, $-1 + 2$, does not equal $-\frac{1}{2}$. The other three expressions are correct.

Would you like further explanation on any step?

Related Questions:

1. Can you simplify fractions like $-\frac{2}{4}$ into their simplest forms?
2. How do you determine the sign of a result when adding or multiplying fractions?
3. What are some common mistakes in evaluating expressions with fractions?
4. How can you verify whether a given value satisfies multiple expressions?
5. Why is subtraction of fractions equivalent to adding their negatives?

Tip:

When working with fractions, always reduce them to their simplest form to check equality more easily!