A (a-2)(a+2)=a (a в квадрате -4)=а в 3 степени -4а
D(y): x=3(равно зачёркивай) или (- знак бесконечности; 3) v (3;+знак бесконечности)
Cos43° Sin(90° - 17°) + Cos(270° - 43°)Sin(180° +17°)=
=Cos43° Cos17° + Sin43° Sin17° = Cos(43° -17°) = Cos26°
168.
а) m*√x/√x*√x = m√x/x
б) 1*√2/√2*√2 = √2/2
в) 3*√c/5√c*√c = 3√c/5c
г) a*√3/2√3*√3 = a√3/2*3 = a√3/6
д) 5*√15/4√15*√15 = 5√15/4*15 = 5√15/60 = √15/12
169.
а) 4*(√3-1)/(√3+1)*(√3-1) = 4(√3-1)/√3-1 = 4
в) 1*(√х+√у)/(√х+√у)*(√х-√у) = √х+√у/х-у
д) 33*(7+3√3)/(7-3√3)*(7+3√3) = 33*(7+3√3)/49-27 = 3*(7+3√3)/2 = 21+9√3/2
б) 1*(1+√2)/(1-√2)*(1+√2) = 1+√2/1-2 = 1+√2/-1 = -1-√2
г) а(√а-√b)/(√a-√b)*(√a+√b) = a(√a-√b)/a-b
e) 15*(2√5-5)/(2√5+5)*(2√5-5) = 15*(2√5-5)/20-25 = -6√5 + 15
![\left \{ {{x+2y=4} \atop {3x-4y=2}} \right. \ =\ \textgreater \ x=4-2y](https://tex.z-dn.net/?f=+%5Cleft+%5C%7B+%7B%7Bx%2B2y%3D4%7D+%5Catop+%7B3x-4y%3D2%7D%7D+%5Cright.++%5C+%3D%5C+%5Ctextgreater+%5C++x%3D4-2y)
подставляем во второе ур-е
![3(4-2y)-4y=2 \\ 12-6y-4y=2 \\ 10y=10 \\ y=1 \\ \\ x=4-2y \\ x=4-2*1 =4- 2= 2](https://tex.z-dn.net/?f=3%284-2y%29-4y%3D2+%5C%5C+12-6y-4y%3D2+%5C%5C+10y%3D10+%5C%5C+y%3D1+%5C%5C++%5C%5C+x%3D4-2y+%5C%5C+x%3D4-2%2A1+%3D4-+2%3D+2+)
y=1
x=2
![\left \{ {{2x-3y=2} \atop {4x-5y=1}} \right. \ =\ \textgreater \ 2x=2+3y](https://tex.z-dn.net/?f=+%5Cleft+%5C%7B+%7B%7B2x-3y%3D2%7D+%5Catop+%7B4x-5y%3D1%7D%7D+%5Cright.+%5C+%3D%5C+%5Ctextgreater+%5C+2x%3D2%2B3y)
![x= \frac{2+3y}{2}](https://tex.z-dn.net/?f=x%3D+%5Cfrac%7B2%2B3y%7D%7B2%7D+)
![4x-5y=1 \\ \\ 4(\frac{2+3y}{2} )-5y=1 \\ 2(2+3y)-5y=1 \\ 4+6y-5y=1 \\ y=-3 \\ \\ x= \frac{2+3y}{2} \\ x= \frac{2+3*(-3)}{2}= -\frac{7}{2}](https://tex.z-dn.net/?f=4x-5y%3D1+%5C%5C++%5C%5C+4%28%5Cfrac%7B2%2B3y%7D%7B2%7D+%29-5y%3D1+%5C%5C+2%282%2B3y%29-5y%3D1+%5C%5C+4%2B6y-5y%3D1+%5C%5C+y%3D-3+%5C%5C++%5C%5C+x%3D+%5Cfrac%7B2%2B3y%7D%7B2%7D++%5C%5C+x%3D+%5Cfrac%7B2%2B3%2A%28-3%29%7D%7B2%7D%3D+-%5Cfrac%7B7%7D%7B2%7D++)
y=-3
x=-7/2