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

Toán Lớp 8: a) B= 2x(x-3)-(x-5)(x+5) b) C=(x+1)^2 – (x-1)^2 – 3(x+1)(x-1) c) D= 5(x+2)(x-2) – 1/6 (6-8x)^2 +1^7

Toán Lớp 8: a) B= 2x(x-3)-(x-5)(x+5)
b) C=(x+1)^2 – (x-1)^2 – 3(x+1)(x-1)
c) D= 5(x+2)(x-2) – 1/6 (6-8x)^2 +1^7

Comments ( 2 )

  1. Giải đáp:
    a)B=x²-6x+25
    b)C=-3x²+4x+3
    c)D=-17/3x²+16x-25
    Lời giải và giải thích chi tiết:
    a)B=2x(x-3)-(x-5)(x+5)
        =2x²-6x-(x²-25)
        =2x²-6x-x²+25
        =x²-6x+25
    b)C=(x+1)²-(x-1)²-3(x+1)(x-1)
           =x²+2x+1-(x²-2x+1)-3(x²-1)
           =x²+2x+1-x²+2x-1-3x²+3
           =(x²-x²-3x²)+(2x+2x)+(1-1+3)
           =-3x²+4x+3
    c)D=5(x+2)(x-2)-1/6(6-8x)²+1^7
           =5(x²-4)-1/6(36-96x+64x²)+1
           =5x²-20-6+16x-32/3x²+1
           =(5x²-32/3x²)+16x+(-20-6+1)
          =-17/3x²+16x-25

  2. a)B=2x(x-3)-(x-5)(x+5)
         =2x²-6x-x²+25
         =x²-19
    b)C=(x+1)²-(x-1)²-3(x+1)(x-1)
         =x²+2x+1-x²+2x-1-3x²+3
         =-3x²+4x+3
    c)D=5(x+2)(x-2)-$\frac{1}{6}$(6-8x)²+$1^{7}$ 
          =5x²-20-$\frac{32}{3}$x²+16x-6+1
          =-$\frac{17}{3}$x²+16x-25
     

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