3.
\((1)\)化简:\((a{-}2){⋅}\dfrac{a^{2}{-}4}{a^{2}{-}4a{+}4}{=}\)______.
\((2)(3a{+}3b{+}1)(3a{+}3b{-}1){=}899\),则\(a{+}b{=}\)______
\((3)\) 当\(x{=}\)______ 时,分式\(\dfrac{x^{2}{-}1}{x^{2}{+}x{-}2}\)的值为零.
\((4)\) 如果多项式\(x^{2}{+}mx{+}9\)是一个完全平方式,则\(m\)的值是______ .
\((5)\) 若\(\dfrac{1}{x}{-}\dfrac{1}{y}{=}2\),则\(\dfrac{2x{+}3xy{-}2y}{x{-}2xy{-}y}\)的值是______ .