Toán Lớp 8: Thực hiện phép tính
x+9 / x^2-9 – 3 / x^2+3x
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Toán Lớp 8: Thực hiện phép tính
x+9 / x^2-9 – 3 / x^2+3x
Comments ( 2 )
Giải đáp:
#Clickbim
$\dfrac{x+9}{x²-9}$ – $\dfrac{3}{x²+3x}$ (ĐK : x \ne 0 ; x \ne +-3)
= $\dfrac{x+9}{(x-3)(x+3)}$ – $\dfrac{3}{x(x+3)}$
= $\dfrac{x(x+9)}{x(x-3)(x+3)}$ – $\dfrac{3(x-3)}{x(x+3)(x-3)}$
= $\dfrac{x²+9x}{x(x-3)(x+3)}$ – $\dfrac{3x-9}{x(x-3)(x+3)}$
= $\dfrac{x²+9x-3x+9}{x(x-3)(x+3)}$
= $\dfrac{x²+(9x-3x)+9}{x(x-3)(x+3)}$
= $\dfrac{x²+6x+9}{x(x-3)(x+3)}$
= $\dfrac{x²+3.2x+3²}{x(x-3)(x+3)}$
= $\dfrac{(x+3)²}{x(x-3)(x+3)}$
= $\dfrac{x+3}{x(x-3)}$
Lời giải và giải thích chi tiết:
(x+9 )/( x^2-9 ) -( 3) /( x^2+3x)(xne0;xne+-3)
=(x+9 )/( (x-3)(x+3) ) -( 3) /( x(x+3))
=(x(x+9)-3(x-3))/(x(x-3)(x+3))
=(x^2+9x-3x+9)/(x(x-3)(x+3))
=(x^2+6x+9)/(x(x-3)(x+3))
=(x+3)^2/(x(x-3)(x+3))
=(x+3)/(x(x-3))