( √7 - √12)( √ 7 - 3√3)=(√7)^2- 3√21-√84+3√36=7-3√21 - √84+12=19-3√21 - 2√21=19-<span>√21</span>
2c(9-p²)= 2c(3-c)(3+c)
3k(y²-1)= 3k(y-1)(y+1)
3(x²-25a²)= 3(x-5a)(x+5a)
-2a(y²-a²)= -2a(y-a)(y+a)= 2a(a-y)(y+a)
5x(x²-a²)= 5x(x-a)(x+a)
bc(c²-b²)= bc(c-b)(c+b)
Sinx/cosx>cosx/cosx
tgx>1
π/4+πk<x<π/2+πk
Ответ: 4+1=5
Объяснение: (2x-9y=-1)*5 (5x+y=21) *-2
10х-45у=-5 -10х-2у=-42
10х-45у-10х-2у=-5-42
-47у=-47
У=1
5х+1=21
5х=21-1
5х=20
х=4