The Arrhenius equation
k = Ae^(-Ea/RT)
k = rate constant
A = another constant
R = gas constant: 8.31 JK-1mol-1
T = temperature (K)
Ea = activation energy (J)
You don't have to memorise the equation, you just have to understand how it works and the relationship between the factors.
1. As Ea increases, k decreases. Therefore, a large activation energy means a slow rate of reaction.
2. As T increases, so does k. Therefore, at higher temperatures, the rate is faster.