EQUAL SQUARE ROOT

  K= +4/7     or    K=  - 4/7

K^2=16/49 take the sqrt of both sides

K=4/7

The first thing you should recognize about 16/49 is that both the numerator and denominator of that fraction are perfect squares. Which means you can very easily take the square root ... like this:

${k}^{2} = \frac{16}{49}$

$\sqrt{{k}^{2}} = k = \frac{\sqrt{16}}{\sqrt{49}} = \frac{4}{7}$

The final asnwer is 4/7. (or -4/7)