Решите уравнение: 9x^2+42x+49=0.

\[9x² + 42x + 49 = 0\]

\[D = 42^{2} - 4 \cdot 9 \cdot 49 =\]

\[= 1764 - 1764 = 0\]

\[x = \frac{- 42 \pm \sqrt{0}}{2 \cdot 9} = - \frac{42}{18} = - \frac{7}{3} =\]

\[= - 2\frac{1}{3}\]

\[Ответ:\ x = - 2\frac{1}{3}.\]