Q)
If \( \overrightarrow a = 4\hat i + 5\hat j - \hat k, \overrightarrow b = \hat i - 4\hat j + 5\hat k, \overrightarrow c = 3\hat i + \hat j - \hat k, \) find a vector \( \overrightarrow d\) , which is perpendicular to both \( \overrightarrow a \: and \: \overrightarrow b \: and \: \overrightarrow d.\overrightarrow c = 21 \).
...
