`5x + 10 . 4x - 8 . (\frac{90-5x}{16x})= 5/2`
Giải thích:
`5x + 10 . 4x - 8 . (\frac{90-5x}{16x})= 5/2`
`=5x + 10 . 4x - 8 . (\frac{90}{16x}-\frac{5x}{16x})= 5/2`
`=5x + 10 . 4x - 8 . (45/8x-5/16)= 5/2`
`=5x+40x- 45x + 40/16 = 5/2`
`=5/2=5/2.`
`\frac{x^3-x^2}{1-x^2}=\frac{x^2(x-1)}{(1-x)(x+1)}=\frac{-x^2(1-x)}{(1-x)(x+1)}=\frac{-x^2}{x+1}.`
Vậy cần điền vào là: `-x^2.`