What is the number 6.3 x 10^-4 written in decimal notation?

The number 6.3 x 10^-4 in decimal notation is 0.00063.

To write 6.3 x 10^-4 in decimal notation, you need to move the decimal point four places to the left.

To convert a number written in scientific notation (6.3 x 10^-4) to decimal notation, you need to move the decimal point to the left or right based on the exponent.

In this case, the exponent is -4, which means you need to move the decimal point 4 places to the left.
Starting with 6.3, move the decimal point four places to the left and fill in any empty spaces with zeros.

Therefore, 6.3 x 10^-4 in decimal notation is 0.000063.