To determine which of the given expressions is not a function, we apply the vertical line test: if a vertical line can intersect the graph of the relation at more than one point, then it is not a function.
Let's analyze each equation:
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\(y = 3x + 5\): This is a linear equation and represents a straight line. It passes the vertical line test, so it is a function.
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\(y = \pm x\sqrt{}\): This is ambiguous as written, but it suggests two separate equations: \(y = x\) and \(y = -x\). Together, these represent two straight lines that are symmetric about the origin. A vertical line can intersect both lines at the same x-value, meaning this is not a function.
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\(y = x\): This is a linear equation and represents a straight line that passes through the origin. It passes the vertical line test, so it is a function.
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\(y = 5x\): This is also a linear equation representing another straight line. It also passes the vertical line test, so it is a function.
Thus, the equation that is not a function is \(y = \pm x\sqrt{}\).