Maths Question:
$\text{If }{{U}_{1}}=-1,\text{ }{{U}_{2}}=-5\text{ and }{{U}_{n}}=a+bn,\text{ find }a,b\text{ and }{{U}_{5}}$
Maths Solution:
$\begin{align} & {{U}_{1}}=-1=a+b----(i) \\ & {{U}_{2}}=-5=a+2b---(ii) \\ & \text{Subtract (i) from (ii)} \\ & b=-4 \\ & \text{substitute }b=-4\text{ into equation(i)} \\ & -1=a-4 \\ & a=3 \\ & {{U}_{n}}=3-4n \\ & \therefore {{U}_{5}}=3-4(5)=3-20=-17 \\ \end{align}$
University mathstopic: