TITLE: how this equation is a linear equation?
QUESTION [5 upvotes]: How is the equation $x_1+5x_2-\sqrt{(2x_3)} = 1$
 a linear equation? The answer given in the book is, "The Equation is linear".
How can an equation involving a square root like the above equation be a linear equation?
here is the cutting of the book,

REPLY [13 votes]: Here is the real exercise found on Amazon...