A variable electric current is given by $t = t ^ { 2 } - 7 t + 14$ , where t is in seconds. At what time is the current i is equal to 4 A.
A) At times 2 and 5 seconds the current i is equal to 4 A.
B) At times 3 and 4 seconds the current i is equal to 4 A.
C) At times 4 and 5 seconds the current i is equal to 4 A.
D) At times 2 and 2.5 seconds the current i is equal to 4 A.
E) At time 2 seconds the current i is equal to 4 A.

Question

Quizplus · Accepted Answer

To find when the current $i$ is equal to 4 A, we set the given equation equal to 4 and solve for $t$: $i = t^2 - 7t + 14 = 4$. Rearranging gives $t^2 - 7t + 10 = 0$, which factors to $(t-2)(t-5) = 0$, yielding solutions $t = 2$ and $t = 5$ seconds.

A Variable Electric Current Is Given By t=t2−7t+14t = t ^ { 2 } - 7 t + 14t=t2−7t+14

A Variable Electric Current Is Given By $t = t ^ { 2 } - 7 t + 14$