arithmetic
posted by Anonymous .
the sum of irst and the fourthterm of a linear squence is10 and the sum of its thired and seventh term is 20.find the common difference and the first term

The nth term of a linear sequence is a + (n1)d
T1 + T4 = a + a+3d = 10
T3 + T7 = a+2d + a+6d = 20
2a + 3d = 10
2a + 8d = 20
5d = 10
d=2
a=2