8:1 Multiplexer With 5 Parameters of F(A,B,C,D,E) = ABCD +B'CDE+BC'D'
The approach you're taking only works if you have a 32:1 multiplexer with 5 select inputs.

If what you have is an 8:1 multiplexer with 3 select inputs, you need to get creative. Note that inputs A and E only appear in one term each, and they're never inverted. This means that you can connect BCD to the select inputs (B is the MSB) and create the desired function by connecting A to the 7 input and E to the 3 input. You also need to tie the 4 input high and all other inputs low.







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