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

Toán Lớp 8: tìm x biết a) (3x+4)^2-(3x-1)(3x+1)=49 b) x^2-4x+4=9(x-2) c) x^2-25=3x-15 d) (x-1)^3+3(x+1)^2=(x^2-2x+4)(x+2) e) x^2-4x+4-(x-2)(x+2)=0

Tháng Sáu 14, 2022 Toán học 1 Comment 0 views

Toán Lớp 8: tìm x biết
a) (3x+4)^2-(3x-1)(3x+1)=49
b) x^2-4x+4=9(x-2)
c) x^2-25=3x-15
d) (x-1)^3+3(x+1)^2=(x^2-2x+4)(x+2)
e) x^2-4x+4-(x-2)(x+2)=0
f) 7x^2=14x=0
g) (5x+2)^2=(3x-7)^2
h) x^2-8x=-16
giúp em ạ

Comments ( 1 )

  1. quynhthanhnghi
    quynhthanhnghi
    14 Tháng Sáu, 2022 at 11:32 sáng
    Reply
    a) (3x+4)^2-(3x-1)(3x+1)=49
    (3x)^2 + 2.3x.4 + 4^2 – (3x)^2 – 1 = 49
    9x^2 + 24x +16 – (9x^2 – 1) = 49
    9x^2 + 24x +16 – 9x^2 +1 = 49
    9x^2 – 9x^2 + 24x + ( 16 + 1) = 49
    24x + 17 = 49
    24x = 49 – 17 = 32
    x = 32 / 24 = 4 / 3
    b) x^2-4x+4=9(x-2)
    x^2 – 4x + 4 = 9x – 18
    x^2 – 4x + 4 – (9x – 18) = 0
    x^2 – 4x + 4 – 9x + 18 = 0
    x^2 + ( -4x – 9x ) + ( 4 + 18 ) = 0
    x^2 – 13x + 22 = 0
    ????^2 − 2???? − 11???? + 22 = 0
    (x^2 – 2x) – ( 11x – 22) = 0
    x( x – 2 ) – 11 ( x – 2 ) = 0
    ( x – 2 ) ( x – 11 ) = 0
    <=> x – 2 = 0 <=> x = 2
    <=> x – 11 = 0 <=> x = 11
    Vậy x = { 2; 11}
    c) x^2-25=3x-15
    x^2 – 25 – (3x – 15) = 0
    x^2 – 25 – 3x + 15 = 0
    x^2 – 3x + ( – 25 + 15 ) = 0
    x^2 – 3x – 10 = 0
    ????^2 + 2???? − 5???? − 10 = 0
    (x^2 + 2x ) – ( 5x + 10 ) = 0
    x ( x + 2 ) – 5 ( x + 2 ) = 0
    ( x + 2 ) ( x – 5 ) = 0
    <=> x + 2 = 0 <=> x = -2
    <=> x – 5 =0 < = > x = 5
    Vậy x = {-2; 5}
    Bạn có nhiều bài quá nên mình không làm hết được bạn thông cảm
    Đánh giá 5 sao giúp mình nhaa

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

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