2(3а-8b)-4(-a+3b)
6a-16b+4a-12b
10a-28b
при a=2,7 b=-2
10(2,7)-28(-2)=27+56=83
8(х-3)^+16x=8x^-48x+72+16x=8x^-32x+72
(y-5)^-(y+7)^=y^-10y+25-y^-14y-49=-24y-59
(m-4)(m+4)+m(5-m)=m^-16+5m-m^=5m-16
(x-8)^-(x-3)(x+3)=x^-16x+64-x^-9=-16x+55
(8x-1)(8x+1)=4x(16x+1)-2
64x^-1=64x^+4x-2
64x^-64x^-4x=-2+1
4x=1
x= 1/4 или 0,25
2cos²x + cosx - 1=0
Замена:
t=cosx
t²=cos²x
2t²+t-1=0
D=1² -4*2*(-1)=1+8=9=3²
t₁=(1-3)/4=-1/2
t₂=(1+3)/4=4/4=1
При t= -1/2
cosx= -1/2
x= (+/-) 2п/3 + 2пn, n∈Z;
При t=1
cosx=1
x=2пn, n∈Z.
Ответ: 2пn, n∈Z;
(+/-)2п/3 +2пn, n∈Z.