If the nth term of an arithmetic progression is given by 19 - 6n, then what is the sum of the first 33 terms of the AP?
1 Answer
Jun 27, 2018
Explanation:
#"using the formula for sum to n terms"#
#•color(white)(x)S_n=n/2[2a+(n-1)d]#
#"where a is the first term and d the common difference"#
#"we require to find both a and d"#
#"using the nth term formula"#
#a=19-(6xx1)=13#
#a_2=19-(6xx2)=7#
#d=a_2-a=7-13=-6#
#S_(33)=33/2[(2xx13)+(32xx-6]#
#color(white)(xx)=33/2(26-192)#
#color(white)(xx)=33/2xx-166=-2739#
