Toán Lớp 8: Thực hiện phép tính:
a) 1-9x²/x²+4x : 2-6x/3x
b) y³+8/y-1 : (y²-2y+4)
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Toán Lớp 8: Thực hiện phép tính:
a) 1-9x²/x²+4x : 2-6x/3x
b) y³+8/y-1 : (y²-2y+4)
Comments ( 1 )
Giải đáp:
a, (1 – 9x^2)/(x^2 + 4) : (2 – 6x)/(3x) (x \ne 0; -4; 1/3)
= [(1 – 3x).(1 + 3x)]/[x.(x + 4)] . [3x]/(2.(1 – 3x))
= [(1 – 3x).(1 + 3x).3x]/[2x.(x + 4).(1 – 3x)]
= [3.(1 + 3x)]/[2.(x + 4)]
= [3 + 9x]/[2x + 8]
$\\$
b, (y^3 + 8)/(y – 1) : (y^2 – 2y + 4) (y \ne 1)
= [(y + 2).(y^2 – 2y + 4)]/[y – 1] . 1/[y^2 – 2y + 4]
= [(y + 2).(y^2 – 2y + 4)]/[(y – 1).(y^2 – 2 + 4)]
= (y + 2)/(y – 1)
$#dairana$