ghê

\(\dfrac{-x^2+2xy-y^2}{x+y}=\dfrac{A}{y^2-x^2}\)

<=> \(\dfrac{-\left(-x^2+2xy-y^2\right)}{y+x}=\dfrac{A}{y^2-x^2}\)

<=> \(\dfrac{x^2-2xy+y^2}{y+x}=\dfrac{A}{y^2-x^2}\)

<=> \(\dfrac{\left(y-x\right)\left(x-y\right)^2}{y^2-x^2}=\dfrac{A}{y^2-x^2}\)

<=> A = (y - x)(x - y)²

???

b. \(\dfrac{x-3}{x^2+x+1}=\dfrac{P}{x^3-1}\)

<=> \(\dfrac{\left(x-3\right)\left(x-1\right)}{x^3-1}=\dfrac{P}{x^3-1}\)

<=> P = (x - 3)(x - 1)

a. \(\dfrac{A}{x-2}=\dfrac{5x^2+13x+6}{x^2-4}\)

<=> \(\dfrac{A\left(x+2\right)}{x^2-4}=\dfrac{5x^2+13x+6}{x^2-4}\)

<=> A(x + 2) = 5x² + 10x + 3x + 6

<=> A(x + 2) = 5x(x + 2) - 3(x + 2)

<=> A(x + 2) = (5x - 3)(x + 2)

<=> A = \(\dfrac{\left(5x-3\right)\left(x+2\right)}{x+2}\)

<=> A = 5x - 3

27cm

ok bn

\(\left(\dfrac{1}{7}\right)^2.\dfrac{1}{7}.\dfrac{1}{49^2}\)

= \(\dfrac{1}{49}.\dfrac{1}{7}.\dfrac{1}{2401}\)

= \(\dfrac{1}{823543}\)