Числитель и знаменатель умножаем на
1) (y - 4)(y + 2) - (y - 2)^2 = y^2 - 2y - 8 - y^2 + 4y - 4 = 2y - 12 = 2(y - 6)
2) <span>3х³у³-3х⁴у²+9х²у² = 3xy(xy - x^2 + 3)</span>
1) 2x + 3y = 3 | 5 10x + 15y = 15
+
5x - 4y = 19 | - 2 - 10x + 8y = - 38
_______________
23y = - 23
y = - 1
2x + 3 * (-1) = 3
2x - 3 = 3
2x = 6
x = 3
Ответ: (3 ; - 1)
2) a + b = 22
+
a - b = 3
_________
2a = 25
a = 12.5
12,5 + b = 22
b = 22 - 12,5
b = 9,5
D1=(a+1)^2-(3a+7)=a^2+2a+1-3a-7=a^2-a-6>0,
a^2-a-6=0,
a1=-2, a2=3,
a∈(-∞;-2)U(3;+∞)