Question

S29, если a1 = 28, d = -2

Answer 1

$a_{1}=28\\\\d=-2\\\\S_{29}=\frac{2a_{1}+28d }{2}*29=(a_{1}+14d)*29=(28+14*(-2))*29=\\\\=(28-28)*29=0 \\\\\boxed{S_{29}=0}$