А) а-в+к+н
в) -а+в+с-д
б) -а+б-с
г) м-н-р+к
я русскими набирала
1. y=(x-1)/2; xy+y=(-1+x)(x+1)/2=-0.5+0.5x²=12; - 1+x²=24; x(1)=-5 => y(1)=-3, x(2)=5 => y(2)=2.
2. b=a+7; a²+b²=a²+49+14a+a²=2a²+14a+49=169; 2a²+14a=120; a²+7a-60=0. По теореме Виета: a(1)+a(2)=-7, a(1)a(2)=-60 => a(1)=-12 => b(1)=-5, a(2)=5 => b(2)=12
<span> (sin (3x/2)+ cos(3x\2))^2=1\2</span>
<span>sin^2(3x/2)+2sin3x/2cos3x/2+cos^2(3x/2)=1/2</span>
<span>1+sin3x=1/2</span>
<span>sin3x=-1/2</span>
<span>3x=(-1)^(n+1)*pi/6+pi n</span>
<span>x=(-1)^(n+1)*pi/18+1/3pi n</span>
1)80³-50³=(8*10)³-(5*10)³=10³(8³-5³)=1000(8-5)(8²+8*5+5²)=<span><span>300*10(8²+8*5+5²)
</span> 2)87</span><span>³+32</span>³=(87+32)(87²-87*32+32²)=119(87²-87*32+32²)
3)75³+65³=(5*15)<span>³+(5*13)</span>³=5³(15³+13³)=5*25(15+13)(15²-15*13+13²)=
5*25*28(15²-15*13+13²)=700*5<span><span>(15²-15*13+13²)
</span>4)84³+24³ =.(12*7)³+(12*2)³=12³(7³+2³)=2³6³(7+2)(7²-7*2+2²)=8*216*9</span><span>(7²-7*2+2²)=</span>8*1944<span>(7²-7*2+2²)</span>
b1=9
q=-2
b2= 9×(-2)= -18
b3= -18×(-2)=36