What is a radical, and how is it expressed mathematically?

\( x + 5 y \)

(i) \( 2.25 \% \) of \( x \) is 630

Simplify the following: (1) \( \frac{x-1}{x^{2}+3 x+2} \div\left[\frac{x-3}{x+1}-\frac{x-4}{x+2}\right] \) (2) \( \frac{\frac{6 x+5}{x-5}}{\frac{3 x+20}{x-5}+2} \) (3) \( \frac{a^{2}+\left(1-a^{2}\right)}{(1+a) a} \times \frac{(1+a) a}{a^{2}-\left(1-a^{2}\right)} \)

\( \left. \begin{array} { l }{ y - 29 = 81 } \\ { y - 29 + \ldots = 81 + 29 } \\ { y = } \end{array} \right. \)

Example Solve the equation \( 2 x^{2}+4 x-10=0 \) with error precision 0.05