a)`ĐKXĐ:` `x ≠0 ; x ≠-5`
b) `P= (x^2 + 2x)/(2x + 10) + (x - 5)/x + (50 - 5x)/(2x(x+5))`
`=(x^2 + 2x)/(2(x + 5)) + ((x - 5).2.(x+5))/(2x(x+5)) + (50 - 5x)/(2x(x+5))`
`=((x^2 + 2x)x)/(2(x + 5)) + (2(x^2 - 25))/(2x(x+5)) + (50 - 5x)/(2x(x+5))`
`=(x^3 + 2x^2)/(2(x + 5)) + (2x^2 - 50)/(2x(x+5)) + (50 - 5x)/(2x(x+5))`
`=(x^3 + 2x^2 + 2x^2 - 50 + 50 - 5x)/(2x(x+5))`
`=(x^3 + 4x^2 - 5x)/(2x(x+5))`
`=(x^3 - x^2 + 5x^2 - 5x)/(2x(x+5))`
`=(x^2(x-1)+5x(x-1))/(2x(x+5))`
`=((x-1)x(x-5))/(2x(x+5))`
`=(x-1)/2`
`P=1`
`⇔(x-1)/2=1`
`⇔x-1=2`
`⇔x=3(TM)`
`P=3`
`⇔(x-1)/2=3`
`⇔x-1=6`
`⇔x=7(TM)`
