1, x(x-1)-x ²=3 2, (x-3)x-x ²=-7 3, (x-5)(x-4)-x ²=-1 4, (2x+1)(x-2)-2x ²=3 5, (x-2)(x+2)-x ²=20 6, (x-5)(2x-1)-2x ²=8

0 bình luận về “1, x(x-1)-x ²=3 2, (x-3)x-x ²=-7 3, (x-5)(x-4)-x ²=-1 4, (2x+1)(x-2)-2x ²=3 5, (x-2)(x+2)-x ²=20 6, (x-5)(2x-1)-2x ²=8”

1. `1. x(x-1)-x^2=3`

   `⇔x^2-x-x^2=3`

   `⇔-x=3`

   `⇔x=-3`

   `2. (x-3)x-x^2=-7`

   `⇔ x^2-3x-x^2=-7`

   `⇔ -3x=-7`

   `⇔ x=7/3`

   `3. (x-5)(x-4)-x^2=-1`

   `⇔ x^2-9x+20-x^2=-1`

   `⇔-9x=-1-20=-21`

   `⇔ x=21/9=7/3`

   `4. (2x+1)(x-2)-2x^2=3`

   `⇔ 2x^2-x-2-2x^2=3`

   `⇔ -x-2=3`

   `⇔ -x=3+2=5`

   `⇔ x=-5`

   `5. (x-2)(x+2)-x^2=20`

   `⇔ x^2-2^2-x^2=20`

   `⇔ -2x^2=20`

   `⇔ 4=20(KTM) `

   `6. (x-5)(2x-1)-2x^2=8`

   `⇔ (x-5)(2x-1)-2x^2=8`

   `⇔ 2x^2-15x+5-2x^2=8`

   `⇔ -15x+5=8`

   `⇔ -15x=8-5=3`

   `⇔ x=3:(-15)=-1/5`

    

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2. `1. x(x-1)-x^2=3`

   `⇔x^2-x-x^2=3`

   `⇔-x=3`

   `⇔x=-3`

   `2. (x-3)x-x^2=-7`

   `⇔ x^2-3x-x^2=-7`

   `⇔ -3x=-7`

   `⇔ x=7/3`

   `3. (x-5)(x-4)-x^2=-1`

   `⇔ x^2-9x+20-x^2=-1`

   `⇔-9x=-1-20=-21`

   `⇔ x=21/9=7/3`

   `4. (2x+1)(x-2)-2x^2=3`

   `⇔ 2x^2-x-2-2x^2=3`

   `⇔ -x-2=3`

   `⇔ -x=3+2=5`

   `⇔ x=-5`

   `6. (x-5)(2x-1)-2x^2=8`

   `⇔ (x-5)(2x-1)-2x^2=8`

   `⇔ 2x^2-15x+5-2x^2=8`

   `⇔ -15x+5=8`

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