- #26

- 17

- 1

##a^2+b^2\neq 0## isn't this assuming that ##a## and ##b## are purely real which isn't implied in the question?We have ##a\cdot (a^2+b^2)=0## and ##a^2+b^2\neq 0.## That is the same as ##x\cdot 2= 0##. Just as if ##a^2+b^2## was ##2## and ##a## was ##x##. It isn't, but it is the same situation.