expalin EPI with K MAP HERE.??

Question

Consider the Boolean expression f(A,B,C,D) = Σm (0, 1, 2, 5, 7, 8, 10, 12,
14, 15). Find the possible number of essential prime Implicants .??

Comments

Which test series is this?

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made easy

Answer 1

sorry i hav not equipment to drow this so to cover green color 1 there are two only possible way to group these green 1's so EPI are 

(a)B'D'

(b)AC'D'

SO ONLY 2 EPI

Comments

how is  AC'D' a essential prime implicant.
i mean there that ABC'D' can also be paired by rolling the map
and it can be paired with ABCD'.
so since there are multiple ways to pair ABC'D' , so AC'D' should NOT be Essential prime implicant

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Only two epi,  b'd' and ad'

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https://gateoverflow.in/?qa=blob&qa_blobid=12544361520368197834

why can't these four become essential prime implicants

Answer 2

refer to this

http://www.cs.columbia.edu/~cs6861/handouts/quine-mccluskey-handout.pdf

http://web.stcloudstate.edu/pkjha/CSCI220/KarnaughMap.pdf

Comments

how is  AC'D' a essential prime implicant.
i mean there that ABC'D' can also be paired by rolling the map
and it can be paired with ABCD'.
so since there are multiple ways to pair ABC'D' , so AC'D' should NOT be Essential prime implicant