Question

A1, a2 , a3....... in AP such that a3 + a5 + a8 = 11 and a4 + a2 = -2 then a1 + a6 + a7 =______

Answer 1

Answer:

given,

A1,A2,....are in Ap,

let the common difference be d,

therefore,the series will be,

A1,A1+d,A1+2d,.....,

given,

A3+A5+A8 = 11,

=>A3+ (A3+2d) + (A3+5d) = 11,

=> 3A3 + 7d = 11,----->eqn1,

also given that,

A4+A2 = -2,

=>(A3+d) + (A3-d) = -2,

=> 2A3 = -2

=> A3 = -1

substitute A3=-1 in eqn 1,

=>3(-1)+7d = 11,

=> 7d = 14,

=> d = 2.

A1 = A3-2d = -1-2(2) = -5,

A6 = A3+3d = -1+3(2) = 5,

A7 = A3+4d = -1+4(2) = 7.

A1+A6+A7 = -5+5+7 = 7.

Hope it helps u...