Which expression is equivalent to `210x^{2}\ -\ 63x`?
The expression equivalent to `210x^{2}\ -\ 63x` can be simplified by factoring out the common factor of 21x:
`210x^{2}\ -\ 63x = 21x(10x\ -\ 3)`
Therefore, the equivalent expression is `21x(10x\ -\ 3)`.