Question

a6-? d-? если a5+a7=54 a2=39

Answer 1

$a_{6} =frac{a_{5}+a_{7}}{2}=frac{54}{2}=27\\left { {{a_{6}=27 } atop {a_{2}=39 }} right.\\-left { {{a_{1}+5d=27 } atop {a_{1}+d=39 }} right.\\-------\\4d=-12\\d=-3$