Môn Toán Lớp 8 Tìm x biết 25x ²-9=0 (x-3) ²-4=0 x ²-2x=24 (x+4) ²-(x+1)(x-1)=16 (2x-1) ²+(x+3) ²-5(x+7)(x-7) (6x-2) ²+(5x-2) ²-4(3x-1)(5x-2) 3(x-1)

Question

Môn Toán Lớp 8 Tìm x biết
25x ²-9=0
(x-3) ²-4=0
x ²-2x=24
(x+4) ²-(x+1)(x-1)=16
(2x-1) ²+(x+3) ²-5(x+7)(x-7)
(6x-2) ²+(5x-2) ²-4(3x-1)(5x-2)
3(x-1) ²-3x(x-5)=1
(x-2 )³-x ²(x-6)=4
(x-1)(x ²+x+1)-x(x+2)(x-2)=5
(x-1) ³-(x+3)(x ²-3x+9)+3(x ²-4) Giúp em bài này với ạ em cần gấp, đừng copy nguồn trên mạng nha. Em xin cảm ơn thầy cô và các bạn nhiều.

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Madelyn 11 tháng 2022-04-08T11:25:50+00:00 2 Answers 0 views 0

Trả lời ( )

  1. myngoc
    1
    2022-04-08T11:27:13+00:00
    Reply

    25x²-9=0

    ⇔25x²=9

    ⇔5x=√9=3 hoặc 5x=-√9=-3

    ⇔x=3/5 hoặc x=-3/5 

    (x-3)²-4=0

    ⇔(x-3)²=4

    ⇔x-3=√4=2 hoặc x-3=-√4=-2

    ⇔x=2+3=5 hoặc x=-2+3=1

    x²-2x=24

    ⇔ x²-2x-24=0

    ⇔(x+4)(x-6)=0

    ⇔x=-4 hoặc x=6

    (x+4)²-(x+1)(x-1)=16

    ⇔x²+8x+16-x²+1-16=0

    ⇔8x=-1

    ⇔x=-1/8

    (2x-1)²+(x+3)²-5(x+7)(x-7)=0

    ⇔4x²-4x+1+x²+6x+9-5x²+245=0

    ⇔2x+255=0

    ⇔x=-255/2

    (6x-2) ²+(5x-2) ²-4(3x-1)(5x-2)=0

    ⇔36x²-24x+4+25x²-20x+4-60x²+44x-8=0

    ⇔x²=0

    ⇔x=0

    3(x-1) ²-3x(x-5)=1

    ⇔3x²-6x+3-3x²+15x-1=0

    ⇔9x+2=0

    ⇔x=-2/9

    (x-2)³-x²(x-6)=4

    ⇔x³-6x²+12x-8-x³+6x²-4=0

    ⇔12x-12=0

    ⇔x=1

    (x-1)(x²+x+1)-x(x+2)(x-2)=5

    ⇔x³-1-x³+4x-5=0

    ⇔4x-6=0

    ⇔x=6/4=3/2

    (x-1)³-(x+3)(x²-3x+9)+3(x²-4)=0

    ⇔x³-3x²+3x-1-x³-27+3x²-12=0

    ⇔3x-40=0

    ⇔x=40/3

    Chúc bạn học tốt

  3. haianh
    0
    2022-04-08T11:27:40+00:00
    Reply

    Đáp án:

     

    Giải thích các bước giải:

    $25x^2-9=0$

    $⇔(5x-3)(5x+3)=0$

    ⇔\(\left[ \begin{array}{l}5x-3=0\\5x+3=0\end{array} \right.\) 

    ⇔\(\left[ \begin{array}{l}x=\dfrac{3}{5}\\x=-\dfrac{3}{5}\end{array} \right.\) 

    $(x-3)^2-4=0$

    $⇔(x-3-2)(x-3+2)=0$

    $⇔(x-5)(x-1)=0$

    ⇔\(\left[ \begin{array}{l}x=5\\x=1\end{array} \right.\) 

    $x^2-2x=24$

    $⇔x^2-2x-24=0$

    $⇔x^2-6x+4x-24=0$

    $⇔(x-6)(x+4)=0$

    ⇔\(\left[ \begin{array}{l}x=6\\x=-4\end{array} \right.\) 

    $(x+4)^2-(x+1)(x-1)=16$

    $⇔x^2+8x+16-x^2+1=16$

    $⇔8x=16-17$

    $⇔8x=-1$

    $⇔x=-\dfrac{1}{8}$

    $(2x-1)^2+(x+3)^2-5(x+7)(x-7)=0$

    $⇔4x^2-4x+1+x^2+6x+9-5(x^2-49)=0$

    $⇔5x^2+2x+10-5x^2+245=0$

    $⇔2x=-255$

    $⇔x=-\dfrac{255}{2}$

    $(6x-2)^2+(5x-2)^2-4(3x-1)(5x-2)=0$

    $⇔36x^2-24x+4+25x^2-20x+4-12x(5x-2)+4(5x-2)=0$

    $⇔61x^2-44x+8-60x^2+24x+20x-8=0$

    $⇔x^2=0$

    $⇔x=0$

    $3(x-1)^2-3x(x-5)=1$

    $⇔3(x^2-2x+1)-3x^2+15x=1$

    $⇔3x^2-6x+3-3x^2+15x=1$

    $⇔9x=1-3$

    $⇔9x=-2$

    $⇔x=-\dfrac{2}{9}$

    $(x-2)^3-x^2(x-6)=4$

    $⇔x^3-6x^2+12x-8-x^3+6x^2=4$

    $⇔12x=12$

    $⇔x=1$

    $(x-1)(x^2+x+1)-x(x+2)(x-2)=5$

    $⇔x^3-1-x(x^2-4)=5$

    $⇔x^3-1-x^3+4x=5$

    $⇔4x=6$

    $⇔x=\dfrac{3}{2}$

    $(x-1)^3-(x+3)(x^2-3x+9)+3(x^2-4)=0$

    $⇔x^3-3x^2+3x-1-x^3-27+3x^2-12=0$

    $⇔3x-40=0$

    $⇔3x=40$

    $⇔x=\dfrac{40}{3}$

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