Q.$\bar a$ and $\bar b$ are non-collinear vectors. If $\bar c = (x-2)\bar a + \bar b$ and $\bar d = (2x+1)\bar a - \bar b$ are collinear, then find the value of $x$.

For a vector a and a real number (scalar) k, the vector ka has magnitude |k||a| and points in the same direction as a when k>0, the opposite direction when k<0, and is the zero vector when k=0; in particular the unit vector along a is a-hat = a/|a|, and a vector of any desired length k along a's direction is k times that unit vector. Because ka is always parallel to a, scalar multiplication gives the standard algebraic test for two non-zero vectors a and b to be collinear (parallel): they are collinear exactly when a = m b for some non-zero scalar m, equivalently w …