Hello!
Let's solve each alternative:
a.
[tex]\begin{gathered} 3\sqrt{5-7} \\ 3\sqrt{-2} \end{gathered}[/tex]
indefinite in R, because there isn't a square root of a negative number.
b.
[tex]\begin{gathered} 4-\sqrt{15} \\ 4-3.87 \\ 0.13\text{ approximately} \end{gathered}[/tex]
c.
[tex]\begin{gathered} \sqrt{20}-8 \\ 4.47-8 \\ -3.53\text{ approximately} \end{gathered}[/tex]
d.
[tex]\begin{gathered} 1-2\sqrt{10} \\ 1-2(3.16) \\ 1-6.32 \\ -5.32\text{ approximately} \end{gathered}[/tex]
Answer:
Last alternative.
