A) sin²a-cos²a=sin²a-1+sin²a=2sin²a-1
b) tg²a-ctg²a=
![\frac{sin^2a}{cos^2a}- \frac{cos^2a}{sin^a}= \frac{1-cos^2a}{cos^2a}- \frac{cos^2a}{1-cos^2a}=](https://tex.z-dn.net/?f=+%5Cfrac%7Bsin%5E2a%7D%7Bcos%5E2a%7D-+%5Cfrac%7Bcos%5E2a%7D%7Bsin%5Ea%7D%3D+%5Cfrac%7B1-cos%5E2a%7D%7Bcos%5E2a%7D-+%5Cfrac%7Bcos%5E2a%7D%7B1-cos%5E2a%7D%3D++++)
![\frac{(1-cos^2a)^2-cos^4a}{cos^2a(1-cos^2a)}= \frac{1-2cos^2a}{cos^2a(1-cos^2a)}](https://tex.z-dn.net/?f=+%5Cfrac%7B%281-cos%5E2a%29%5E2-cos%5E4a%7D%7Bcos%5E2a%281-cos%5E2a%29%7D%3D+%5Cfrac%7B1-2cos%5E2a%7D%7Bcos%5E2a%281-cos%5E2a%29%7D++)
<span>(x+3) + (x+3) = 6
х+3+х+3=6
2х+6=6
2х=0
х=0
Ответ: х=0
</span>
4800/48=100, 6*100=600kg slivok
600/40=15, 15*8=120kg masla
120/24=5, 5*18=90
Ответ:90кг масла
X²-15x-16=0
X1*x2= 15
X1+x2= -16
X1 = -1
X2= 16