x- арифметическая прогрессия
x2=-2,4
d=1,2
S10-?
Заранее спасибо :)
x2=x1+d,
x1=x2-d=-2.4-1.2=-3.6,
S10=10(2a1+9d)/2=5(2*(-3.6)+9*1.2)=18
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Verified answer
x2=x1+d,
x1=x2-d=-2.4-1.2=-3.6,
S10=10(2a1+9d)/2=5(2*(-3.6)+9*1.2)=18