19. For an A.P. if t4=20 and t7=32, find a, d and tn
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Answer:
a=12
d=4
Step-by-step explanation:
a+(4-1)d=20
a+3d=20............1
a+(7-1)d=32
a+6d=32...........2
subtract 1 from 2
3d=12
d=4
a+3×4=20
a=20-12
a=8
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