Решить пределы функций:

Решение
1) lim x--gt;0 [((7 - x) - (7 + x))*((7 - x) + (7 + x))] / (7 * x) =
= lim x--gt;0  [((7 - x) - ((7 + x))] / (7 * x) = 
 lim x--gt;0 (7 - x - 7 - x) / (7 * x) =  lim x--gt;0 (- 2x) / (7 * x) =
 = - 2 / 7 = - 27 / 7
2)   lim x--gt;-1 [(5+ x) - 2)*((5 + x) + 2)*(8 - x) + 3)] /
 / [((8 - x) - 3)*((8 - x) + 3)*((5 + x) + 2)] = lim x--gt;-1 [(5 + x - 4)*
* (8 - x) + 3)] / [(8 - x - 9) * ((5 + x) + 2)] 
=   lim x--gt;-1 [(1 + x)*((8 - x) + 3)] / [(11 - x)*((5 + x) + 2)] = 0
3)    lim x--gt;4 [(2 - x)*(2 + x)*((6x + 1) + 5) ] / [(6x + 1) - 5)* 
* ((6x + 1) + 5)* (2 + x)] =   lim x--gt;4 [(4 - x)*((6x + 1) + 5) ] /
/ [(6x + 1 - 25)* (2 + x)] = lim x--gt;4 [(4 - x)*((6x + 1) + 5)] /
/  [6*(x - 4)* (2 + x) = - lim x--gt;4 [(4 - x)*((6x + 1) + 5)] /
  [6*(4 - x)* (2 + x)] =  - lim x--gt;4 [((6x + 1) + 5)] /  [6* (2 + x)] = 10/24 =
= 5 /12
4)  lim x--gt; -1 [(x + 20) - 4)*((x + 20) + 4)] / (x+ 64) = 
 lim x--gt; - 1 (x + 20 - 16) / (x+ 64) = lim x--gt; - 1 (x + 4) / [(x+ 4)*(x - 4x + 16)] = lim x--gt; -1  [1 / (x - 4x + 16)] = 1/21
5)  lim x--gt; 3 (2x- 3x - 9) / [(x - 2) - (4 - x)] = 
2x - 3x - 9 = 0
D = 9 + 4*2*9 = 81
x = (3 - 9)/4 = - 3/2
x = (3 + 9)/4 = 3
 lim x--gt; 3 [2*(x + 1,5)*(x - 3)*((x - 2) + (4 - x)] /
 / [((x - 2) - (4 - x)) * ((x - 2) + (4 - x))] =  
lim x--gt; 3 [2*(x + 1,5)*(x - 3)*((x - 2) + (4 - x))] / (x - 2 - 4 + x) =
= lim x--gt; 3 [2*(x + 1,5)*(x - 3)*((x - 2) + (4 - x))] / [2*(x - 3)] =
= lim x--gt; 3 [2*(x + 1,5)*((x - 2) + (4 - x))] / 2 =
= (2*4,5*2) / 2 = 9