Respuesta :
2.25 x 10^-17. Because it's negative you move the decimal to the left. So 2.5 x 10^-8 is .000000025 and 9 x 10^-10 is .0000000009.
when you multiply scientific notation numbers add the exponents ( -8 + -10 = -18)
now multiply 2.5 *9 = 22.5
so you now have 22.5x10^-18
now make 22.5 a real scientific number by moving the decimal point 1 place to the right, which subtracts 1 from the exponent
so you get:
2.25x10^-17