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

Toán Lớp 8: 1.(3+4x)² -8x(2x-1) =-20 2. (x+3)² – (x+2)² =13 3. (x+1)² – (x+4)² =20 4. (2x+3)² – (2x+5)² =25 5. (5+3x)² -x(9x+3) =18 6. (5x+1)² -25(

Home/ Toán Lớp 8: 1.(3+4x)² -8x(2x-1) =-20 2. (x+3)² – (x+2)² =13 3. (x+1)² – (x+4)² =20 4. (2x+3)² – (2x+5)² =25 5. (5+3x)² -x(9x+3) =18 6. (5x+1)² -25(

Toán Lớp 8: 1.(3+4x)² -8x(2x-1) =-20 2. (x+3)² – (x+2)² =13 3. (x+1)² – (x+4)² =20 4. (2x+3)² – (2x+5)² =25 5. (5+3x)² -x(9x+3) =18 6. (5x+1)² -25(

Tháng Mười Hai 24, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: 1.(3+4x)² -8x(2x-1) =-20
2. (x+3)² – (x+2)² =13
3. (x+1)² – (x+4)² =20
4. (2x+3)² – (2x+5)² =25
5. (5+3x)² -x(9x+3) =18
6. (5x+1)² -25(x+1)² =50
Giúp em mấy câu này với mấy anh chị ạ????

Comments ( 2 )

  1. khanhlanchau
    khanhlanchau
    24 Tháng Mười Hai, 2022 at 2:32 chiều
    Reply
    Giải đáp:
    1.x∈{-29/32}       2.x∈{4}           3.x∈{-35/6}             4.x∈{-41/8}              5.x∈{-7/27}              6.x∈{-37/20}
    Lời giải và giải thích chi tiết:
    1.(3+4x)^2 -8x(2x-1) =-20
    ⇔9+24x+16x^2-16x^2+8x=20
    ⇔3x=-29
    ⇔x=-29/32
    Vậy x∈{-29/32}
    2.(x+3)² – (x+2)² =13
    ⇔x^2+6x+9-x^2-4x-4=13
    ⇔2x+5=13
    ⇔2x=8
    ⇔x=4
    Vậy x∈{4}
    3. (x+1)² – (x+4)² =20
    ⇔x^2+2x+1-x^2-8x-16=20
    ⇔-6x-15=20
    ⇔x=-35/6
    Vậy  x∈{-35/6}
    4. (2x+3)² – (2x+5)² =25
    ⇔4x^2+12x+9-4x^2-20x-25=25
    ⇔-8x-16=25
    ⇔x=-41/8
    Vậy x∈{-41/8}
    5. (5+3x)² -x(9x+3) =18
    ⇔25+30x+9x^2-9x^2-3x=18
    25+27x=18
    x=-7/27
    Vậy x∈{-7/27}
    6. (5x+1)² -25(x+1)² =50
    ⇔25x^2+10x+1-25x^2-50x-25=50
    ⇔-40x-24=50
    ⇔x=-74/40=-37/20
    Vậy x∈{-37/20}

  2. catlantuong
    catlantuong
    24 Tháng Mười Hai, 2022 at 2:32 chiều
    Reply
     1
    (3+4x)^2-8x(2x-1)=-20
    ⇔9+24x+16x^2-16x^2+8x+20=0
    ⇔(9+20)+(24x+8x)+(16x^2-16x^2)=0
    ⇔29+32x=0
    ⇔32x=-29
    ⇔x=-29/32
    Vậy S={-29/32}
    2
    (x+3)^2-(x+2)^2=13
    ⇔x^2+6x+9-(x^2+4x+4)-13=0
    ⇔x^2+6x+9-x^2-4x-4-13=0
    ⇔(x^2-x^2)+(6x-4x)+(9-4-13)=0
    ⇔2x-8=0
    ⇔2x=8
    ⇔x=4
    Vậy S={4}
    3
    (x+1)^2-(x+4)^2=20
    ⇔x^2+2x+1-(x^2+8x+16)-20=0
    ⇔x^2+2x+1-x^2-8x-16-20=0
    ⇔(x^2-x^2)+(2x-8x)+(1-16-20)=0
    ⇔-6x-35=0
    ⇔-6x=35
    ⇔x=-35/6
    Vậy S={-35/6}
    4
    (2x+3)^2-(2x+5)^2=25
    ⇔4x^2+12x+9-(4x^2+20x+25)-25=0
    ⇔4x^2+12x+9-4x^2-20x-25-25=0
    ⇔(4x^2-4x^2)+(12x-20x)+(9-25-25)=0
    ⇔-8x-41=0
    ⇔-8x=41
    ⇔x=-41/8
    Vậy S={-41/8}
    5
    (5+3x)^2-x(9x+3)=18
    ⇔25+30x+9x^2-9x^2-3x-18=0
    ⇔(25-18)+(30x-3x)+(9x^2-9x^2)=0
    ⇔7+27x=0
    ⇔27x=-7
    ⇔x=-7/(27)
    Vậy S={-7/27}
    6
    (5x+1)^2-25(x+1)^2=50
    ⇔25x^2+10x+1-25(x^2+2x+1)-50=0
    ⇔25x^2+10x+1-25x^2-50x-25-50=0
    ⇔(25x^2-25x^2)+(10x-50x)+(1-25-50)=0
    ⇔-40x-74=0
    ⇔-40x=74
    ⇔x=-74/40
    ⇔x=-37/20
    Vậy S={-37/20}

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

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