3 см. так как зар в 4 раза больше, то уровень в 4 раза меньше.
16-4а-а3-а4=(16-а4)-(4а+а3)=(4-а2)*(4+а2)-а*(4+а2)=(4+а2)*((4-а2)*1-а*1)=(4+а2)*(4-а2-а)
X*(x+1)*(x+2)*(x+3) = (x*(x+3))*((x+1)*(x+2)) = ( x^2 +3x)*( x^2 +3x+2) = = 120,
сделаем замену x^2+3x = y, тогда
y*(y+2) =120;
y^2 + 2y - 120 = 0;
D/4 = 1+120 = 121=11^2;
y1 = (-1+11) = 10;
y2 = (-1-11) = -12;
1) x^2 + 3x = 10;
x^2 + 3x - 10 = 0;
D = 9 - 4*(-10) = 49 = 7^2;
x1 = (-3+7)/2 = 4/2 = 2;
x2 = (-3-7)/2 = -10/2 = -5;
2) x^2 + 3x = -12;
x^2 + 3x + 12 = 0;
D = 9 - 4*12 < 0; в 2) решений нет.
Ответ. x1 = 2; x2 = -5;
Ответ:
k=80
b=80
Объяснение:
![\left \{ {{0,3k=0,05b+20} \atop {0,3b=0,2k+8}} \right.](https://tex.z-dn.net/?f=%5Cleft%20%5C%7B%20%7B%7B0%2C3k%3D0%2C05b%2B20%7D%20%5Catop%20%7B0%2C3b%3D0%2C2k%2B8%7D%7D%20%5Cright.)
умножим 2 уравнения на 100
![\left \{ {{30k=5b+2000} \atop {30b=20k+800}} \right.](https://tex.z-dn.net/?f=%5Cleft%20%5C%7B%20%7B%7B30k%3D5b%2B2000%7D%20%5Catop%20%7B30b%3D20k%2B800%7D%7D%20%5Cright.)
![\left \{ {{5b=30k-2000} \atop {30b=20k+800}} \right.](https://tex.z-dn.net/?f=%5Cleft%20%5C%7B%20%7B%7B5b%3D30k-2000%7D%20%5Catop%20%7B30b%3D20k%2B800%7D%7D%20%5Cright.)
![\left \{ {{b=6k-400} \atop {30b=20k+800}} \right.](https://tex.z-dn.net/?f=%5Cleft%20%5C%7B%20%7B%7Bb%3D6k-400%7D%20%5Catop%20%7B30b%3D20k%2B800%7D%7D%20%5Cright.)
![\left \{ {{b=6k-400} \atop {30*(6k-400)=20k+800}} \right.](https://tex.z-dn.net/?f=%5Cleft%20%5C%7B%20%7B%7Bb%3D6k-400%7D%20%5Catop%20%7B30%2A%286k-400%29%3D20k%2B800%7D%7D%20%5Cright.)
![\left \{ {{b=6k-400} \atop {180k-12000-20k=800}} \right.](https://tex.z-dn.net/?f=%5Cleft%20%5C%7B%20%7B%7Bb%3D6k-400%7D%20%5Catop%20%7B180k-12000-20k%3D800%7D%7D%20%5Cright.)
![\left \{ {{b=6k-400} \atop {160k=800+12000}} \right.](https://tex.z-dn.net/?f=%5Cleft%20%5C%7B%20%7B%7Bb%3D6k-400%7D%20%5Catop%20%7B160k%3D800%2B12000%7D%7D%20%5Cright.)
![\left \{ {{b=6k-400} \atop {160k=12800}} \right.](https://tex.z-dn.net/?f=%5Cleft%20%5C%7B%20%7B%7Bb%3D6k-400%7D%20%5Catop%20%7B160k%3D12800%7D%7D%20%5Cright.)
![\left \{ {{b=6k-400} \atop {k=80}} \right.](https://tex.z-dn.net/?f=%5Cleft%20%5C%7B%20%7B%7Bb%3D6k-400%7D%20%5Catop%20%7Bk%3D80%7D%7D%20%5Cright.)
![\left \{ {{b=6*80-400} \atop {k=80}} \right.](https://tex.z-dn.net/?f=%5Cleft%20%5C%7B%20%7B%7Bb%3D6%2A80-400%7D%20%5Catop%20%7Bk%3D80%7D%7D%20%5Cright.)
![\left \{ {{b=80} \atop {k=80}} \right.](https://tex.z-dn.net/?f=%5Cleft%20%5C%7B%20%7B%7Bb%3D80%7D%20%5Catop%20%7Bk%3D80%7D%7D%20%5Cright.)
(х-у)*(2х²-2ху+ух-у²)=(х-у)*(2х²-ху-у²)=2х³-х²у-ху²-2х²у+ху²+у³=2х³-3х²у+у³
это не уравнение, можно только упростить