Determing whether an equation is linear

[delgeezee]

Linear equations do not have roots of variables.
So why are a) and f) linear equations?

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[Jameson]

Hi delgeezee, (Wave)

Welcome to MHB! :)

I agree that if (a) contains $-\sqrt{2x_3}$ then it isn't a linear equation. Perhaps it is a typo and it should be $-\sqrt{2} \hspace{1 mm} x_3$?

Jameson