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

Toán Lớp 8: Bài 2 : Điền vào chỗ trống để có hằng đẳng thức a) (x + 5)2 = b) (3x – 2)2 = c) (x + 4)(x – 4) = d). x2 – 36 = e) (7 + 2x)2 = Bài 3 : R

Toán Lớp 8: Bài 2 : Điền vào chỗ trống để có hằng đẳng thức
a) (x + 5)2 = b) (3x – 2)2 =
c) (x + 4)(x – 4) = d). x2 – 36 =
e) (7 + 2x)2 =
Bài 3 : Rút gọn
a) (3 + 2x)2 + (x – 1)(5x – 2) b) (3 – 2x)2 – (2x – 1)(5x +1)
c) (x + 4)(x – 4) + (2 – 3x)(2 + 3x) d) (5 – x)(5 + x) – (3x +4)(3x – 4)

Comments ( 2 )

  1. Giải đáp:
     
    Lời giải và giải thích chi tiết:
    $\text{Giải đáp : }\left[\begin{matrix} 2)\begin{cases} a ) ( x + 5 )^2 = x^2 + 2 . x .5 + 5^2 = x^2 + 10 x + 25\\b ) ( 3 x − 2 )^2 = ( 3 x )^2 − 2 . ( 3 x ) .2 + 2^2 = 9 x^2 − 12 x + 4\\c ) ( x + 4 ) ( x − 4 ) = x^2 − 4^2 = x^2 − 16\\d ) x^2 − 36 = x^2 − 6^2 = ( x − 6 ) ( x + 6 )\\e ) ( 7 + 2 x ^2 = 7^2 + 2.7 . ( 2 x ) + ( 2 x )^2 = 49 + 28 x + 4x^2\end{cases}\\3)\begin{cases} a ) ( 3 + 2 x )^2 + ( x − 1 ) ( 5 x − 2 ) = 9 x^2 + 5 x + 11\\ b ) ( 3 − 2 x )^2 − ( 2 x − 1 ) ( 5 x + 1 )  = − 6 x^2 − 9 x + 10\\ c ) ( x + 4 ) ( x − 4 ) + ( 2 − 3 x ) ( 2 + 3 x ) = − 8 x^2 − 12\\ d ) ( 5 − x ) ( 5 + x ) − ( 3 x + 4 ) ( 3 x − 4 ) = 25 − 16 − x^2 − 9 x^2 = 9 − 10 x^2\end{cases}\end{matrix}\right.$

  2. a)(x+5)^2
    =x^2+2.x.5+5^2
    =x^2+10x+25
    b)(3x-2)^2
    =(3x)^2-2.(3x).2+2^2
    =9x^2-12x+4
    c)(x+4)(x-4)
    =x^2-4^2
    =x^2-16
    d)x^2-36
    =x^2-6^2
    =(x-6)(x+6)
    e)(7+2x)^2
    =7^2+2.7.(2x)+(2x)^2
    =49+28x+4x^2
    —————————————————————–
    a)(3+2x)^2+(x-1)(5x-2)
    =3^2+2.3.(2x)+(2x)^2+x.5x-x.2-1.5x+1.2
    =9+12x+4x^2+5x^2-2x-5x+2
    =4x^2+5x^2+12x-2x-5x+9+2
    =9x^2+5x+11
    b)(3-2x)^2-(2x-1)(5x+1)
    =3^2-2.3.(2x)+(2x)^2-2x.5x-2x.1+5x.1+1.1
    =9-12x+4x^2-10x^2-2x+5x+1
    =4x^2-10x^2-12x-2x+5x+9+1
    =-6x^2-9x+10
    c)(x+4)(x-4)+(2-3x)(2+3x)
    =(x^2-4^2)+[2^2-(3x)^2]
    =x^2-16+4-9x^2
    =x^2-9x^2-16+4
    =-8x^2-12
    d)(5-x)(5+x)-(3x+4)(3x-4)
    =5^2-x^2-(3x)^2-4^2
    =25-x^2-9x^2-16
    =25-16-x^2-9x^2
    =9-10x^2

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

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