the following expressions with their correct Scientific Notation.

0.000236
397.3 x 10^-1
49
.55 x 10^9
499 x 10^7

0.000236 = 2.36 x 10^-4

397.3 x 10^-1 = 3.973 x 10^2
49 = 4.9 x 10^1
.55 x 10^9 = 5.5 x 10^8
499 x 10^7 = 4.99 x 10^9

are you sure about 49 and 499 x 10^7

Apologies for the mistake. Here are the corrections:

49 = 4.9 x 10^1
499 x 10^7 = 4.99 x 10^9

is 49 4.9 x 10^-1 or that?

Apologies for the confusion. Let me correct the notation for 49:

49 = 4.9 x 10^1

is 4.9 x 10^-1 right too?

Yes, 4.9 x 10^-1 is correct for 0.49 in scientific notation. Thank you for pointing that out.