Toán Lớp 8: cho biểu thức sau:
A=(2x-9)/(x^2-5x+6)-(x+3)/(x-2)-(2x+1)/(3x
rút gọn A?
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Toán Lớp 8: cho biểu thức sau:
A=(2x-9)/(x^2-5x+6)-(x+3)/(x-2)-(2x+1)/(3x
rút gọn A?
Comments ( 1 )
A = (2x-9)/(x^2 – 5x+6) – (x+3)/(x-2) – (2x+1)/(3x)
= (2x-9)/((x-3)(x-2)) – (x+3)/(x-2) – (2x+1)/(3x)
= (2x – 9 – (x+3)(x-3))/((x-3)(x-2)) – (2x+1)/(3x)
= (2x – 9 -(x^2-9))/((x-3)(x-2)) – (2x+1)/(3x)
= (2x- 9 – x^2+9)/((x-3)(x-2)) – (2x+1)/(3x)
= (2x – x^2)/((x-3)(x-2)) – (2x+1)/(3x)
= (-x (x-2))/((x-3)(x-2)) – (2x+1)/(3x)
= (-x)/(x-3) – (2x+1)/(3x)
= (-x . 3x – (2x+1)(x-3))/(3x (x-3))
= (-3x^2 – (2x^2 – 6x + x – 3))/(3x (x-3))
= (-3x^2 – 2x^2 + 6x – x +3)/(3x(x-3))
= (-5x^2 + 5x + 3)/(3x^2 – 9x)