Toán Lớp 8: a) $\frac{x+1}{2x+6}$ +$\frac{2x+3}{x^2+3x}$
b) $\frac{3}{2x+6}$ -$\frac{x-6}{2x^2+6x}$
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Toán Lớp 8: a) $\frac{x+1}{2x+6}$ +$\frac{2x+3}{x^2+3x}$
b) $\frac{3}{2x+6}$ -$\frac{x-6}{2x^2+6x}$
thực hiện phép tính
Comments ( 2 )
=(x+1)/(2(x+3))+(2x+3)/(x(x+3))
MTC:2x(x+3)
=>(x+1)/(2(x+3))=(x(x+1))/(2x(x+3))=(x²+x)/(2x(x+3))
(2x+3)/(x(x+3))=(2(2x+3))/(2x(x+3))=(4x+6)/(2x(x+3))
=(x²+x)/(2x(x+3))+(4x+6)/(2x(x+3))
=(x²+x+4x+6)/(2x(x+3))
=(x²+5x+6)/(2x(x+3))
=(x²+2x+3x+6)/(2x(x+3))
=(x(x+2)+3(x+2))/(2x(x+3))
=((x+3)(x+2))/(2x(x+3))
=(x+2)/(2x)
Vậy (x+1)/(2x+6)+(2x+3)/(x²+3x)=(x+3)/(2x)
b)3/(2x+6)-(x-6)/(2x²+6x)
=3/(2(x+3))-(x-6)/(2x(x+3))
MTC:2x(x+3)
=>3/(2(x+3))=(3x)/(2x(x+3))
=(3x)/(2x(x+3))-(x-6)/(2x(x+3))
=(3x-x+6)/(2x(x+3))
=(2x+6)/(2x(x+3))
=(2(x+3))/(2x(x+3))
=2/(2x)=1/x
Vậy 3/(2x+6)-(x-6)/(2x²+6x)=1/x