Which of the following equations is expressed in scientific notation?

The correct answer is characterized by its format, which adheres to the conventions of scientific notation. Scientific notation expresses numbers as a product of a coefficient and a power of ten. This format allows for the easy representation of very large or very small numbers.

In this case, the option demonstrating scientific notation is written as 1.5 × 10^3. Here, the coefficient (1.5) is a number greater than or equal to 1 and less than 10, and it is multiplied by 10 raised to the power of 3. This indicates that 1.5 is scaled up by a factor of 1000 (or 10^3), which results in 1500 when converted to standard decimal form.

The other choices do not fit the definition of scientific notation. The first option, 0.001234, is a standard decimal and does not have the appropriate power of ten factor. Similarly, while 2.5 × 10^0 and 5.4 × 10^5 are indeed expressed in scientific notation, they represent different numbers. 2.5 × 10^0 equals 2.5, making it straightforward and not particularly large or small. Meanwhile, 5.