Let is:
1v1, sb vs bb, no ante.
Let your opp has 25% range to call and you have J7s.
Now we'll calculate preflop EV for raising to 2.5bb
1. In 25% of cases you will get 1.5bb by fold EV and it is 1.5*0.25= 0.375
2. In 75% of cases our J7s will have nearly 37% EV.
Yours 2.5bb + 1.5bb pot + 1.5bb opp to call.
Pot is 5.5bb, your EV is 37% and you paid 2.5. → 5.5*0.372.5 = 0.465bb.
Multiply it on 75% cases. → 0.465*0.75 =~ 0.349
3. Now get the sum of 1 and 2 it is 0.3750.349= 0.026bb
And you preflop EV is 0.026bb.
Now check it by your formula)
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