Which of the following shows an expression equivalent to the product of two complex numbers, 5i times 4i?

Answer 1

To find an expression equivalent to the product of the two complex numbers \( 5i \) and \( 4i \), we can multiply them directly:

\[ 5i \times 4i = (5 \times 4) \times (i \times i) \]

Calculating the first part:

\[ 5 \times 4 = 20 \]

Now, for the second part, we use the fact that \( i^2 = -1 \):

\[ i \times i = i^2 = -1 \]

Putting it all together:

\[ 5i \times 4i = 20 \times (-1) = -20 \]

Thus, the product \( 5i \times 4i \) is equivalent to \(-20\).