18) \(\dfrac{36t^2}{t(14t+7)(t^2+49)}\)

Разложим \(14t+7=7(2t+1)\) и сократим на \(t\): \(\dfrac{36t^2}{7t(2t+1)(t^2+49)}=\dfrac{36t}{7(2t+1)(t^2+49)}\).

Ответ: \(\dfrac{36t}{7(2t+1)(t^2+49)}\), где \(t\ne0,\;t\ne-\dfrac12\).