-x²+5x+14≥0 |:(-1)
x²-5x-14≤0
(x+2)(x-7)≤0
+ - +
____________________-2________________7_____________
x∈[-2;7]
4x^2=0 | :4
x^2=0/4
x^2=0
x1=0
x2=0
1) а-b+2c(a-b) = a-b+2ca-2cb = a(1+2c)-b(1+2c) =
(a-b)(1+2c)
2) by-3b+2cy+6c = b(y-3)+2c(y+3) = (b+2c)(y²-9)
3) kl-5l-k+5 = k(l-1)-5(l-1) = (k-5)(l-1)
4) 3ab-2ac+4cd-6bd = 3b(a-2d)-2c(a-2d) = (3b-2c)(a-2d)
5) y²-2by+6b-3y = y(y-3)-2b(y-3) = (y-2b)(y-3)
Очевидно, x лежит в пределах от 486 - 0,5 = 485,5 до 486 + 0,5 = 486,5.