Question

х во 2 - 25 1 х+5
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х+6 х во 2 +5х х во 2 - 6х



х+3 ( х+3 х-3) при х равно : 1,75. 1,6. -1,6. 0,8. -0,8
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х во2 +9 (х-3 х+3)

Answer 1

$frac{x^2-25}{x+6} * frac{1}{x^2+5x} - frac{x+5}{x^2-6x} = \ \ = frac{(x-5)(x+5) * 1 }{(x+6) * x(x+5) } - frac{x+5}{x(x-6)} = \ \ = frac{x-5}{x(x+6)} - frac{x+5}{x(x-6)} = \ \ = frac{(x-5)(x-6) - (x+5)(x+6)}{x(x+6)(x-6)} = \ \ = frac{x^2-6x-5x+30 - x^2-6x-5x-30}{x(x^2-6^2)} = \ \ = frac{-22x}{x(x^2-36)} = - frac{22}{x^2-36}$
Ответ :  4)


$frac{x+3}{x^2 + 9 } * ( frac{x+3}{x-3} + frac{x-3}{x+3} )= \ \ = frac{x+3}{x^2 + 9} * frac{(x+3)(x+3) + (x-3)(x-3)}{(x-3)(x+3)} = \ \ = frac{x+3}{x^2 + 3^2} * frac{(x+3)^2 +(x-3)^2}{x^2 - 3^2} = \ \ = frac{x+3}{x^2 + 3^2} * frac{x^2 +6x+3^2 + x^2 -6x+3^2}{(x^2-3^2)} = \ \ = frac{(x+3)(2x^2+18)}{(x^2+9)(x^2-9)} = frac{2(x+3)(x^2+9)}{(x^2+9)(x+3)(x-3)} = \ \ = frac{2}{x-3} \ \ x=1.75 \ frac{2}{1.75 - 3} = frac{2}{-1.25} = -1.6$
Ответ:  2)