Explain why the square root of a number is defined to be equal to that number to the 1/2 power.

The square root of a number is a number, when multiplied by itself, equals a desired value.

See below for proof

The square root of a number n, is represented as:

This can be rewritten as:

According to law of indices

Using the above rule, we have:

Hence, the square root of a number is the same as the number to the power of 1/2

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the answer is y < -3 or   y > 3

-3y > 7 + 2

-3 y > 9

y < -3