Rearrange the equation to isolate E:
M=

m • v^2 / 2  = E

Step-by-step explanation:

m = 2E/v^2

multiply each side by v^2

m • v^2 = 2E

divide each side by 2

m • v^2 / 2  = E

addition

step-by-step explanation:

δabc ≅ δdcb by sas because

db ≅ ac . . given (side)

bc ≅ bc . . reflexive property (side)

∠dbc ≅ ∠ acb . . alternate interior angles where transversal bc crosses parallel lines bd and ac (included angle)