Register Now

Login

Lost Password

Lost your password? Please enter your email address. You will receive a link and will create a new password via email.

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

Toán Lớp 8: rút gọn biểu thức a)3x(3x-4y)-9x(x-3y) b)x(2x-1)(4x+3)+(2x-1)^3 c)(x-2y)^3-(x-3y)^3+5xy-(x-3y)^3(3x+y) d)(3x-2)^2+3(x-1)(x+1)-(4x+1)(3x

Tháng Mười Một 13, 2022 Toán học 1 Comment 0 views

Toán Lớp 8: rút gọn biểu thức
a)3x(3x-4y)-9x(x-3y)
b)x(2x-1)(4x+3)+(2x-1)^3
c)(x-2y)^3-(x-3y)^3+5xy-(x-3y)^3(3x+y)
d)(3x-2)^2+3(x-1)(x+1)-(4x+1)(3x+1)

Comments ( 1 )

  1. tuyethutanhthu
    tuyethutanhthu
    13 Tháng Mười Một, 2022 at 10:14 sáng
    Reply
    Giải đáp:
     a, 3x(3x – 4y) – 9x(x – 3y)
    = 9x^2 – 12xy – 9x^2 + 27xy
    = (9x^2 – 9x^2) + (-12xy + 27xy)
    = 15xy
    b, x(2x – 1)(4x + 3) + (2x – 1)^3
    = (2x^2 – x)(4x + 3) + (2x)^3 – 3.(2x)^2 .1 + 3.2x.1^2 – 1^3
    = 8x^3 + 6x^2 – 4x^2 – 3x + 8x^3 – 12x^2 + 6x – 1
    = (8x^3 + 8x^3) + (6x^2 – 12x^2 – 4x^2) + (-3x + 6x) – 1
    = 16x^3 – 10x^2 + 3x – 1
    c, (x – 2y)^3 – (x – 3y)^3 + 5xy – (x – 3y)^3 (3x + y)
    = x^3 – 3.x^2 .2y + 3.x.(2y)^2 – (2y)^3 –  [x^3 – 3.x^2 .3y + 3.x.(3y)^2 – (3y)^3] + 5xy – [x^3 – 3.x^2 .3y + 3.x.(3y)^2 – (3y)^3](3x + y)
    = x^3 – 6x^2 y + 12xy^2 – 8y^3 – (x^3 – 9x^2 y + 27xy^2 – 27y^3) + 5xy – (x^3 – 9x^2 y + 27xy^2 – 27y^3)(3x + y)
    = x^3 – 6x^2 y + 12xy^2 – 8y^3 – x^3 + 9x^2 y – 27xy^2 + 27y^3 + 5xy – (3x^4 + x^3 y – 27x^3 y – 9x^2 y^2 + 81x^2 y^2 + 27xy^3 – 81xy^3 – 27y^4)
    = x^3 – 6x^2 y + 12xy^2 – 8y^3 – x^3 + 9x^2 y – 27xy^2 + 27y^3 + 5xy – 3x^4 – x^3 y + 27x^3 y + 9x^2 y^2 – 81x^2 y^2 – 27xy^3 + 81xy^3 + 27y^4
    = (x^3 – x^3 ) + (-6x^2 y + 9x^2 y) + (12xy^2 – 27xy^2) + (-8y^3 + 27y^3) + 5xy – 3x^4 + (-x^3 y + 27x^3 y) + (9x^2 y^2 – 81x^2 y^2) + (-27xy^3 + 81xy^3 ) + 27y^4
    = 3x^2 y – 15xy^2 + 19y^3 + 5xy – 3x^4 + 26x^3 y – 72x^2 y^2 + 54xy^3 + 27y^4
    d, (3x – 2)^2 + 3(x – 1)(x + 1) – (4x + 1)(3x + 1)
    = (3x)^2 – 2.3x.2 + 2^2 + 3(x^2 – 1^2) – (12x^2 + 4x + 3x + 1)
    = 9x^2 – 12x + 4 + 3x^2 – 3 – 12x^2 – 4x – 3x – 1
    = (9x^2 + 3x^2 – 12x^2) + (-12x – 4x – 3x) + (4 – 3 – 1)
    = -19x

Leave a reply

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

Ngọc

About Ngọc