To solve the equation \( 21x^2 + 14x = 0 \), we can factor out the common term:
\[ 7x(3x + 2) = 0 \]
Setting each factor equal to zero gives us:
- \( 7x = 0 \) which simplifies to \( x = 0 \)
- \( 3x + 2 = 0 \) which simplifies to \( 3x = -2 \) or \( x = -\frac{2}{3} \)
Thus, the solutions to the equation are \( x = 0 \) and \( x = -\frac{2}{3} \).
Looking at the provided answer options, the correct choice is:
B. \( 0 \) and \( -\frac{2}{3} \).