`\text{ gọn biểu thức:}`
`A = (x^2 – 5)(x + 3) + (x + 4)(x – x^2)`
`= x^2.(x + 3) + (–5).(x + 3) + x.(x – x^2) + 4.(x – x^2)`
`= x^2.x + x^2.3 + (–5).x + (–5).3 + x.x + x.(–x^2) + 4.x + 4.(–x^2)`
`= x^3 + 3x^2 – 5x – 15 + x^2 – x^3 + 4x – 4x^2`
`= (x^3 – x^3) + (3x^2 + x^2 – 4x^2) + (4x – 5x) – 15`
`= –x – 15.`
`a) \text{Nếu} x = 0 \yext{thì} A = –0 – 15 = –15`
`b) \text{Nếu }x = 15 \text{thì} A = –15 – 15 = –30`
`c) \text{Nếu} x = –15 \text{thì }A = –(–15) – 15 = 15 – 15 = 0`
`d) \text{Nếu} x = 0,15 \text{thì} A = –0,15 – 15 = –15,15`
`\text{Tuyển thành viên}`
