Question

qual o décimo termo de uma PA(a+b,2a+4b,..)?

Answer 1

Sabemos que:

([a+b]+4b)/2=2a
a+b+4b=2.2a
a+5b=4a
5b=4a-a
5b=3a
b=3a/5

a1=a+b
a1=a+(3a/5)
a1=(5a/5)+(3a/5)
a1=(5a+3a)/5
a1=8a/5

a2=2a

r=a2-a1
r=2a-(8a/5)
r=(10a/5)-(8a/5)
r={10a-8a)/5
r=2a/5

a2=2a
n=10
r=2a/5
a10=?

an=am+(n-m)r
a10=a2+(10-2)(2a/5)
a10=2a+8(2a/5)
a10=2a+(16a/5)
a10=(10a/5)+(16a/5)
a10=(10a+16a)/5
a10=26a/5
a10=(5a+21a)/5
a10=(5a/5)+(21a/5)
a10=a+(7.3a)/5
a10=a+7(3a/5)
###a10=a+7b