Question

find the sum of 19 terms of the AP whose nth term is given by tn=7-4n

Answer 1

The sum of 19 terms of this AP is -627
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Answer 2

Answer: t1=7-4.1=3

t2=7-4.2=-1

t3=7-4.3=-5

t4=7-4.4=-9

t5=7-4.5=-13

t6=7-4.6=-17

t7=7-4.7=-21

t8=7-4.8=-25

t9=7-4.9=-29

t10=7-4.10=-33

t11=7-4.11=-37

t12=7-4.12=-41

t13=7-4.13=-45

t14=7-4.14=-49

t15=7-4.15=-53

t16=7-4.16=-57

t17=7-4.17=-61

t18=7-4.18=-65

t19=7-4.19=-69

now sum of 19 terms =t1+t2+.....+t18+t19=-627

Step-by-step explanation: