Answer:
-4.8
Explanation:
You want the negative square root of 23.
Square root
23 is not a perfect square, so you will likely need a calculator to find its square root. The calculator can also negate it for you and do the rounding.
-√23 ≈ -4.8
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Additional comment
There are some methods for approximating the square root. One of them writes the number in the form s²+r, where s² is the largest perfect square less than the number. Here, that would be 23 = 4² +7, with s=4, r=7.
Then an approximation of the square root will be s +r/(2s+1) = 4 +7/9 ≈ 4.78. For the purpose here, this is close enough to get you to the correct "rounded to tenths" value.
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