A1=-375
a2=-75
d=a2-a1=-75+375=300
S5=(a1+4a)*5/2=(-375+1200)*5/2=825*5/2=4125/2=2062,5
<span>2(x-y) \ x(y-x) =
= -2(у-х) </span><span>\ х(у-х) =
= минус за дробью 2 </span><span>\ х</span>
<span>(m-1)(m²-7m)+(m-1)(5m+1) =(m-1)(m²-7m+5m+1)=(m-1)(m²-2m+1)=
=(m-1)(m-1)²=(m-1)³</span>
<span> ((-1)</span><span>^2)</span><span>^5-1^2=0
<span>(-1)^7+(-1)^4=0</span></span>