(Х+8)(7х+5)=(Х+8)(5х+7)
7x^2+5x+56x+40=5x^2+7x+40x+56
2x^2+14x-16=0/:2
X^2+7x-8=0
D=49-4*1*(-8)=81
X1=-7+9/2=1
X2=-7-9/2=-8
5) (x-3) (x-2)/(x-3)=x-2
6) (x+3) (x-2)/(x+3)=x-2
1) 3(x-1)(x-1/3)/x-1/3=3(x-1)=3x-3
3) (x-4) (x-3)/(x-4)=x-3
8) (x-3)(x-1)/(x-3)=x-1
остальные сам попробуй
7) (a^2+4-a^2-2+a*sqrt(2))/(a+sqrt(2))(a^2+2-asqrt(2))*(a^2+2-asqrt(2))/sqrt(2))=
=(2+asqrt(2))/(a+sqrt(2))*1/sqrt(2)=sqrt(2)/sqrt(2)=1
ответ 2)
3)
сosx/sinx=-1/5
sinx=y
25=26y^2
sinx=5/sqrt(26) cosx=-1/sqrt(26)
cos2x=1/26-25/26=-24/26
sin2x=-10/26
2+12-2,6=11,4=57/5
ответ 4)
1). 3/10-1/15=(9-2)/30=7/30; 2).7/30*3=7/10. Ответ: 7/10.