Which discovery by astronomer Vera Rubin helped prove the existence of dark matter? HELP MEEEH :c

Galaxies exist outside of the Milky Way.
The expansion of the universe is accelerating.
Galaxies spin faster than they should, based on their visible matter.
Gas giants form farther from the Sun, where temperatures are cooler.

Galaxies spin faster than they should based on their visible matter

Step-by-step explanation:

Hope this helps :)

step-by-step explanation:

5=812a+9+3

step 1: simplify both sides of the equation.

5=812a+9+3

5=(812a)+(9+3)(combine like terms)

5=812a+12

5=812a+12

step 2: flip the equation.

812a+12=5

step 3: subtract 12 from both sides.

812a+12−12=5−12

812a=−7

step 4: divide both sides by 812.

812a /812 = -7/812

a= -1/116

so the answer is

a=   -1/116