For problems #11 through #20 you can only use the following 5 formulas. Also give your answers as a decimal to 3 decimal places. Any other formulas such as summation for n2 is not allowed. This is what using an app is going to use which means if you try to use an app or website it will use a process that is not covered until a higher class and you will get marked wrong for the problem. Find the formula for the nth term for the arithmetic sequence where a1= -23 and d=31