7x^2-21=0
x^2-3=0
(x-3)(x+3)=0
x= +3;-3
X-2 ≤ -6.25/(x+3)
(x-2)*(x+3) ≤6.25
x² + 3x -2x -6 ≤6.25
x² +x -6 ≤ 6.25
x² + x ≤ 6.25 +6
x² +x ≤12.25
x(x + 1) ≤12.25
x ≤12.25 или х≤11.25
(b-a) (-a-b) +2b² = (-a-b)(b-a) +2b²=
=- (b+a)(b-a) +2b²= -(b²-a²) +2b²=
= a²-b²+2b²=a²+b²
1)
x1 * x2 = 36, x1 + x2 = 5
x1 = 9, x2 = -4
2)
x1 * x2 = 15/32, x1 + x2 = 44/32
Тут не знаю...