A21=a1+20*d
a21=-10+20*(-3)
a21=-10-60
a21=-70
1-2sin^2(45°+1,5a)=cos(2(45°+1,5a))=cos(90°+3a)=-sin(3a)=-(3sina-4sin^3a)=4sin^3a-3sina
Уравнение -x^2-10*x-23=0 <span>x = -sqrt(2)-5 </span><span>x=−<span>2√</span>−5
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2x-12+3x=5-x+1
5x-12=6-x
5x+x=6+12
6x=18
x=18/6
x=3
(11a-b)²+(9a+7b)(8a-13b)=121a²+b²-22ab+72a²-117ab+56ab-91b²=193a²-90b²-83ab