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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 7: P(x) = x3 – 6x + 2 Q(x) = 2×2 – 4×3 + x – 5 a) Tính P(x) + Q(x) b) Tính P(x) – Q(x)

Toán Lớp 7: P(x) = x3 – 6x + 2
Q(x) = 2×2 – 4×3 + x – 5
a) Tính P(x) + Q(x)
b) Tính P(x) – Q(x)

Comments ( 2 )

  1. a)P(x)+Q(x)=(x^3-6x+2)+(2x^2-4x^3+x-5)
                              =x^3-6x+2+2x^2-4x^3+x-5
                              =(x^3-4x^3)+(2x^2)+(-6x+x)+(2-5)
                              =-3x^3+2x^2-5x+7
    b)P(x)-Q(x)=(x^3-6x+2)-(2x^2-4x^3+x-5)
                              =x^3-6x+2-2x^2+4x^3-x+5
                              =(x^3+4x^3)-2x^2+(6x+x)+(2+5)
                              =5x^3-2x^2-7x+7
     

  2. Giải:
    a, P(x) + Q(x)
    = (x^3 – 6x + 2) + (2x^2 – 4x^3 + x – 5)
    = x^3 – 6x + 2 + 2x^2 – 4x^3 + x – 5
    = (x^3 – 4x^3) + 2x^2 – (6x – x) + (2 – 5)
    = -3x^3 + 2x^2 – 5x – 3
    b, P(x) – Q(x)
    = (x^3 – 6x + 2) – (2x^2 – 4x^3 + x – 5)
    = x^3 – 6x + 2 – 2x^2 + 4x^3 – x + 5
    = (x^3 + 4x^3) – 2x^2 – (6x + x) + (2 + 5)
    = 5x^3 – 2x^2 – 7x + 7
     

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222-9+11+12:2*14+14 = ? ( )