would 64974000345 be written 6.4*10^10

or 6.4974*10^10
2) how would you write 7.991*10-10 in scientific notation?
3) does 9.0 have 2 (sf) and 100.0000 have (7sf)?I'm confused about the trailing zeros when it comes to decimal points.These are trailing zeros.
4) What do you mean when you said we do not add powers with different exponents?
5) What is the difference between powers and exponents?
6) h^8*h-^3*h^0=h^5. I thought 0 is 1 exponent!

1. If all the digits are significant, then is it is written 6.47974000345*10^10

2. It is in scientific notation already.
3. 2sf, and 7 sf.
4. you do add powers with different exponents, but not powers of different bases.
5. no difference.
6. 0 is an exponent,but when adding, it does not change the result a^6*a^0=a^6

remember anything to the zero power is ONE. 45^0=1; a^0=1