If three vectors \(\vec{p},\ \vec{q}\ \ and\ \ \vec{r}\) are represented by \(\hat{i}\ +\ a\hat{j}\ \), \(2\hat{i}\ -\ \sqrt{7}\hat{k}\) and \(2\hat{i}\ +\ 4\hat{j}\ -\ \sqrt{5}\hat{k}\) and \(|\vec{p}\ +\ \ \vec{q}|\ =\ |\vec{r}|\) the value of a will be:
1
± 5
2
± 3
3
± 7
4
None of these