the fifth and tenth term of an Ap are 0 and 10 respectively.find the twentieth term
Tn=a + (n-1)d
T5=a +(5-1)d
0 =a + (4)d...eqn 1
T10 = a +(10 -1)d
10 =a + 9d...eqn 2
Subtract eqn 1 from 2
10 =a + 9d
-0 =a + 4d
10 = 5d
d = 2
Put d= 2
0 =a + (4)2
0 = a +8
a = 0 - 8
a = -8
Tn = a + (n -1)d
T20=-8 +(20 -1) X 2
= -8 + 38
= 30
It correct
Xn = a + d(n-1)
10= a + d(9)
0 = a + d(4)
------------- subtract
10 = 5 d
d = 2
a = -8
so
X20 = -8 + 2*19 = 30