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

Toán Lớp 8: thực hiện phép tính a,– 3x(x + 2)^2 + (x + 3)(x – 1)(x + 1) – (2x – 3)^2 b, (6x+1)^2 + (6x-1)^2 – 2(1+6x)(6x –1) c, (x – 2)(x^2 + 2x +

Tháng Mười Hai 30, 2022 Toán học 1 Comment 0 views

Toán Lớp 8: thực hiện phép tính
a,– 3x(x + 2)^2 + (x + 3)(x – 1)(x + 1) – (2x – 3)^2
b, (6x+1)^2 + (6x-1)^2 – 2(1+6x)(6x –1)
c, (x – 2)(x^2 + 2x + 4) – (x – 1)^3 + 7

Comments ( 1 )

  1. ngoclanhoa
    ngoclanhoa
    30 Tháng Mười Hai, 2022 at 1:46 sáng
    Reply
    Giải đáp:
    $a)$ $-2x^3-13x^2-x-12$
    $b$) $4$
    $c)$ $3x^2-3x$
    Lời giải và giải thích chi tiết:
    $a)$ $-3x\left(x+2\right)^2+\left(x+3\right)\left(x-1\right)\left(x+1\right)-\left(2x-3\right)^2$
    $=-3x^3-12x^2-12x+\left(x+3\right)\left(x-1\right)\left(x+1\right)-\left(2x-3\right)^2$
    $=-3x^3-12x^2-12x+x^3-x+3x^2-3-\left(2x-3\right)^2$
    $=-3x^3-12x^2-12x+x^3-x+3x^2-3-4x^2+12x-9$
    $=-3x^3+x^3-12x^2+3x^2-4x^2-12x-x+12x-3-9$
    $=-3x^3+x^3-12x^2+3x^2-4x^2-x-3-9$
    $=-3x^3+x^3-12x^2+3x^2-4x^2-x-12$
    $=-2x^3-12x^2+3x^2-4x^2-x-12$
    $=-2x^3-13x^2-x-12$
    $b$) $\left(6x+1\right)^2+\left(6x-1\right)^2-2\left(1+6x\right)\left(6x-1\right)$
    $=36x^2+12x+1+\left(6x-1\right)^2-2\left(1+6x\right)\left(6x-1\right)$
    $=36x^2+12x+1+36x^2-12x+1-2\left(1+6x\right)\left(6x-1\right)$
    $=36x^2+12x+1+36x^2-12x+1-72x^2+2$
    $=36x^2+36x^2-72x^2+12x-12x+1+1+2$
    $=12x-12x+1+1+2$
    $=1+1+2$
    $=4$
    $c)$ $\left(x-2\right)\left(x^2+2x+4\right)-\left(x-1\right)^3+7$
    $=x^3-8-\left(x-1\right)^3+7$
    $=x^3-8-x^3+3x^2-3x+1+7$
    $=x^3-x^3+3x^2-3x-8+1+7$
    $=3x^2-3x-8+1+7$
    $=3x^2-3x$

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

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