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(x-3)²-2x²+18=0
x²-6x+9-2x²+18=0
-x²-6x+27=0
x²+6x-27=0
D=36+108=144,√D=√144=12
x1=(-6+12)/2=6/2=3, x1=3
x2=(-6-12)/2=-18/2=-9, x2=-9
1273. 1) log4(sin(пи/4)); 2) log10(tg(пи/4)); 3) log8(sin(3пи/4))
4) log2(cos(пи/3)); 5) log3(1) -log4(tg(пи/4))*log5(cos(0)).
Решение:
1) log4(sin(пи/4)) = log2²(1/√2) = (1/2)log2(1/2^(1/2))= (1/2)log2(2^(-1/2))=
= (1/2)*(-1/2)log2(2) = -1/4
2) log10(tg(пи/4)) = log10(1) = 0
3) log8(sin(3пи/4)) = log2³(sin(пи/2+пи/4)) =(1/3)log2(cos(пи/4))=
=(1/3)log2(1/√2) = (1/3)log2(1/2^(1/2))= (1/3)log2(2^(-1/2))=(1/3)*(-1/2)log2(2) = -1/6
4) log2(cos(пи/3)) = log2(1/2) = log2(2^(-1)) = -1*log2(2) = -1
5) log3(1) - log4(tg(пи/4))*log5(cos(0)) = 0 - log4(1)*log5(1) = -0*0 = 0
Ответ: 1) -1/4; 2) 0; 3) -1/6; 4) -1; 5) 0.
X^2+x-20>=0
(x+5)(x-4)>=0
D(f)=(-~;-5]U[4;+~)