Answer:
[tex]u = \dfrac{7-\frac{1}{2}at^2}{t}[/tex]
Step-by-step explanation:
[tex]7 = \frac{1}{2}at^2+ut \\\\ ut = 7-\frac{1}{2}at^2 \\ \\ u = \dfrac{7-\frac{1}{2}at^2}{t}[/tex]
