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

Toán Lớp 8: Bài 4.Rút gọn : a) (a-b+c)2+2(a-b+c)(b-c)+(b-c)2 b) (2x-3y+1)2-(x+3y-1)2 c) (3x-4y+7)2+8y(3x-4y+7)+16y2

Tháng Mười Một 2, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: Bài 4.Rút gọn :
a) (a-b+c)2+2(a-b+c)(b-c)+(b-c)2 b) (2x-3y+1)2-(x+3y-1)2
c) (3x-4y+7)2+8y(3x-4y+7)+16y2 d) (x-3)2+2(x-3)(x+3)+(x+3)2
kia là mũ 2 nhé

Comments ( 2 )

  1. catlantuong
    catlantuong
    2 Tháng Mười Một, 2022 at 1:38 chiều
    Reply
    Giải đáp:
    a.(a-b+c)^2+2(a-b+c)(b-c)+(b-c)^2
    = [(a-b+c)+(b-c)]^2
    = [a-b+c+b-c]^2
    = a^2
    b. (2x-3y+1)^2-(x+3y-1)^2
    = [(2x-3y+1)-(x+3y-1)][(2x-3y+1)+(x+3y-1)]
    = [2x-3y+1-x-3y+1][2x-3y+1+x+3y-1]
    = [x-6y+2]xx(3x)
    = 3x^2-18xy+6x
    c. (3x-4y+7)^2+8y(3x-4y+7)+16y^2
    = (3x-4y+7)^2+2xx(4x-4y+7)xx4y+(4y)^2
    = [(3x-4y+7)^2+4y]^2
    = [3x-4y+7+4y]^2
    = [3x+7]^2
    = 9x^2+42x+49
    d. (x-3)^2+2(x-3)(x+3)+(x+3)^2
    = [(x-3)+(x+3)]^2
    = [x-3+x+3]^2
    = x^2

  2. dananhnhu2k4
    dananhnhu2k4
    2 Tháng Mười Một, 2022 at 1:38 chiều
    Reply
    a)(a-b+c)^2+2(a-b+c)(b-c)+(b-c)^2
    =(a-b+c)(a-b+c)+(2a-2b+2c)(b-c)+[b^2 +2b(-c)+(-c)^2]
    =(a-b+c)^{1+1} +(2a-2b+2c)(b-c)+(b^2-2bc+c^2)
    =(a-b+c)(a-b+c)+(2a-2b+2c)(b-c)+(b^2 +2bc+c^2)
    =a^2
    b) (2x-3y+1)^2-(x+3y-1)^2
    =(2x-3y)+1(2x-3y+1)-(x+3y-1)(x+3y-1)
    = 3x(x-6y+2)
    c) (3x-4y+7)^2+8y(3x-4y+7)+16y^2
    =(3x-4y+7)(3x-4y+7)+8y(3x-4y+7)+16y^2
    =9x^2 -24xy+42x+16y^2 -28y-28y+49+8y(3x-4y+7)+16y^2
    =9^2 +42x+49
    d) (x-3)^2+2(x-3)(x+3)+(x+3)^2
    =(x^2 +2x(-3)+(-3)^2 )+(2x-2.3)(x+3)+(x^2 +2x.3+3^2)
    =(x^2 -2x.3+3^2)+(2x-6)(x+3)+(x^2 +2.3x+9)
    =4x^2

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

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