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

Toán Lớp 9: a) (2x-1)(x+7)=x^2-49 b)2x+1/x-3 – x/x+3 =1 c)x+2/3-3x-1/5<-2

Home/ Toán Lớp 9: a) (2x-1)(x+7)=x^2-49 b)2x+1/x-3 – x/x+3 =1 c)x+2/3-3x-1/5<-2

Toán Lớp 9: a) (2x-1)(x+7)=x^2-49 b)2x+1/x-3 – x/x+3 =1 c)x+2/3-3x-1/5<-2

Tháng Hai 10, 2023 Toán học 2 Comments 0 views

Toán Lớp 9: a) (2x-1)(x+7)=x^2-49 b)2x+1/x-3 – x/x+3 =1 c)x+2/3-3x-1/5<-2

Comments ( 2 )

  1. truongankimtrong
    truongankimtrong
    10 Tháng Hai, 2023 at 2:44 sáng
    Reply
    Giải đáp + Lời giải và giải thích chi tiết:
    a)
    (2x-1)(x+7)=x^2-49
    <=> (2x-1)(x+7)-(x^2-49)=0
    <=> (2x-1)(x+7)-(x-7)(x+7)=0
    <=> (x+7)(2x-1-x+7)=0
    <=> (x+7)(x+6)=0
    <=> \(\left[ \begin{array}{l}x+7=0\\x+6=0\end{array} \right.\) <=> \(\left[ \begin{array}{l}x=-7\\x=-6\end{array} \right.\) 
    Vậy S={-7;-6}
    b)
    (2x+1)/(x-3)-x/(x+3)=1 
    ĐKXĐ : x ne +-3
    <=> ((2x+1)(x+3)-x(x-3))/(x^2-9)=(x^2-9)/(x^2-9)
    => (2x+1)(x+3)-x(x-3)=x^2-9
    <=> 2x^2+6x+x+3-x^2+3x-x^2+9=0
    <=> 10x+12=0
    <=> 10x=-12
    <=> x=-6/5 \ \ (tmđk)
    Vậy S={-6/5}
    c)
    (x+2)/3-(3x-1)/5<-2
    <=> (5.(x+2)-3.(3x-1))/15< -30/15
    => 5.(x+2)-3.(3x-1)=-30
    <=> 5x+10-9x+3<-30
    <=> -4x<-30-3-10
    <=> -4x<-43
    <=> x>43/4
    Vậy S={x|x>43/4}

  2. ngoclankhue
    ngoclankhue
    10 Tháng Hai, 2023 at 2:43 sáng
    Reply
    a)(2x-1)(x+7)=x²-49
    ⇔(2x-1)(x+7)=(x+7)(x-7)
    ⇔(2x-1)(x+7)-(x+7)(x-7)=0
    ⇔(x+7)[(2x-1)-(x-7)]=0
    ⇔(x+7)(2x-1-x+7)=0
    ⇔(x+7)(x+6)=0
    ⇔\(\left[ \begin{array}{l}x+7=0\\x+6=0\end{array} \right.\)
    ⇔\(\left[ \begin{array}{l}x=-7\\x=-6\end{array} \right.\)
    Vậy S={-7;-6}
    b)(2x+1)/(x-3)-x/(x+3)=1(ĐKXĐ:x$\neq$ ±3)
    ⇔[(2x+1)(x+3)]/[(x+3)(x-3)]-[x(x-3)]/[(x+3)(x-3)]=[(x+3)(x-3)]/[(x+3)(x-3)]
    ⇒(2x+1)(x+3)-x(x-3)=(x+3)(x-3)
    ⇔2x²+6x+x+3-x²+3x=x²-9
    ⇔(2x²-x²)+(6x+x+3x)+3=x²-9
    ⇔x²+10x+3=x²-9
    ⇔x²+10x-x²=-9-3
    ⇔10x=-12
    ⇔x=-12/10
    ⇔x=-6/5(TM ĐKXĐ)
    Vậy S={-6/5}
    c)(x+2)/3-(3x-1)/5<-2
    ⇔[5(x+2)]/15-[3(3x-1)]/15<-30/15
    ⇒5(x+2)-3(3x-1)<-30
    ⇔5x+10-9x+3<-30
    ⇔5x-9x<-30-10-3
    ⇔-4x<-43
    ⇔x>43/4
    Vậy S={x|x>43/4}

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

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