A particle has initial velocity (ki+4j)(k\mathbf{i}+4\mathbf{j})(ki+4j) m s−1^{-1}−1 and constant acceleration (2i−j)(2\mathbf{i}-\mathbf{j})(2i−j) m s−2^{-2}−2. After 3 s, its displacement from its initial position has magnitude 15 m and has a positive i\mathbf{i}i-component.
Find the value of kkk.