The first term of an arithmetic sequence is 6. the fourth is 21, find the equation for the nth term and find the 18th term

)

1

st term is  

2

and common difference is  

3

2)

1

st term is  

74

and common difference is  

−

10

n

th term of an A.P series is  

T

n

=

a

+

(

n

−

1

)

dStep-by-step explanation:

according to the triangle sum theorem, all the angles in a triangle must add up to 180 degrees. if we know one angle is already 90, we do 180-90=90. the other 2 angles must add up to 90, exactly.

step-by-step explanation: