7х-9у=11 -9у=11-7х у=(7/9)х-(11/9)=(7/9)х-1 2/9
15х-12у=0 12у=15х у=(15/12)х=1,25х
2х+3у=57 3у=57-2х у=19-(2/3)х
A²*sin2π +2ab*cos3π/2 +c³*tg2π = a²*0+2ab*0+c³*0=0+0+0=0
a³*ctg270°+b³*tg0° = a³*0+b³*0= 0+0 =0
|/(42c^5)=c|/(42c)
|/(-50c^5)=5c^2|/(-2c)
|/(8/c^4)=2/c * |/2
#4. а) 9x² - 100 = 0
9x² = 100
x = 10/3
б) (4y - 8)² - (2y+5)² = 0
16² - 64 + 64 - (4y²+20y+25)=0
16y² - 64y + 64 - 4y² -20y - 25 = 0
12y² - 84y + 39 = 0
4y² - 28y + 13 = 0