F=(9.0•10^9 n•m^2/c^2)(3.2•10^-9c)(9.6•10^-9c)/ (.32m)^2 in scientific notation

m^(- 5) = 1/35 → you know that: x^(- a) = 1/x^(+ a) = 1/x^a 

1/m^5 = 1/35 → you take the inverse 

m^5 = 35 

[m^5]^(1/5) = 35^(1/5) → recall: (x^a)^b = x^(ab) 

m^[5 * (1/5)] = 35^(1/5) 

m^[1)] = 35^(1/5) 

m = 35^(1/5) 

The scientific notation is a number between 1 and 9 with few numbers after coma (point) completed by a power 10. 

= [1.4 * 10^(3)] * [2.5 * 10^(- 6)] → you remove the brackets 

= 1.4 * 10^(3) * 2.5 * 10^(- 6) → you order 

= 1.4 * 2.5 * 10^(3) * 10^(- 6) → you make the multiplication 

= 3.5 * 10^(3) * 10^(- 6) → recall: (x^a) * (x^b) = x^(a + b) 

= 3.5 * 10^(3 - 6) 

= 3.5 * 10^(- 3) ← answer C