# Tag Info

Accepted

### If a×b×c×d is 9, what is a+b+c+d ( a b c d are different integers)

If $a, b, c, d$ are distinct integers which satisfies $abcd=9$, find $a+b+c+d$. $a|9, b|9, c|9, d|9$. The factors of $9$ is $-9, -3, -1, 1, 3, 9$. WLOG, $a<b<c<d$. If $a=-9:$ $bcd=-1$ for ...
• 1,674
1 vote
Accepted

### Is this book good for learning math for college physics?

Generally an "engineering mathematics" text is much the same thing as a "physics mathematics" text. There is sometimes more emphasis on something like vectors in physics books but ...
1 vote

### Bolean algebra De morgan's law - can i use it from the outside to the inside like I did?

what is the problem with my solution? The very start. $ABCD+\overline{\overline{A}*\overline{C}+A*\overline{B}+\overline{B*\overline{C}}}$ $ABCD+(A'C'+((AB')')*(B*C'))'$ It should be: \$ABCD+{({A'}{...
• 120k