27/x -(27-7)/(x-3) =10/60 ;
27/x -20/(x-3) =1/6 ;
6*27(x-3) -6*20x =x(x-3) ;
x² -45x +486 =0;
x =(45 ± √(2025 -4*486))/2
x=(45±9)/2 ;
x₁= 18 км/ч ;
<span>x</span>₂<span>= 27 км/ч.</span>
(2/7 - 3/4)·(2/13 - 1/2) = 117/728
1) 2/7 - 3/4 = 8/28 - 21/28 = -13/28
2) 2/13 - 1/2 = 4/26 - 13/26 = -9/26
3) -13/28·(-9/26) = 9·13/28·26 = 117/728
2x - 4(3x + 9) ≥ - 3
2x - 12x - 36 ≥ - 3
- 10x ≥ - 3 + 36
- 10x ≥ 33
x ≤ - 3,3
x ∈ (- ∞ ; - 3,3]
9x^2-42x+49-25=9x^2-42x+24
16-40x+25x^2-64=25x^2-40x-48
2sin²a*cosa/sina= 2sinacosa= sin2a