Homework Statement
Prove that if x^2 + y = 13 and y \neq 4 , then x \neq 3 .Homework Equations
N.A.The Attempt at a Solution
The proof itself is simple enough: suppose x^2 + y = 13 and y \neq 4 . Suppose for the sake of contradiction that x = 3 . Then
\begin{align*}
(3)^2 + y &= 13...
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Ugh, I was starting to suspect I was wasting time because of a typo in the book. I attached the relevant portion of the textbook page as an image, where the above equality is listed along with a couple other vector identities.
Thanks for the extra input (and sanity check).
Homework Statement
(From Plonsey, R. and R. C. Barr, "Bioelectricity: A Quantitative Approach")
Show
\nabla^2 r = 0
given
r = \sqrt{x^2 + y^2 + z^2}.
Homework Equations
\nabla = \frac{\partial}{\partial x}{\bf i} + \frac{\partial}{\partial y}{\bf j} +...