If the first term of AP is 4 and the sum of first five term is equal to one-fourth of the sum of the next five term, then find the 15th term?
5/2 * [2*4 + 4D]=1/4* 5/2 *[8+5D + 9D], solve for D
D = -12 common difference
15th term =[4 + (-12*14)] = - 164
4, -8, -20 , -32 , -44 , -56 , -68 , -80 , -92 , -104 , -116 , -128 , -140 , -152 , -164
