($\frac{1}{3.5}$x – 3)+($\frac{1}{5.7}$x – 5)+($\frac{1}{7.9}$x – 7)+…+($\frac{1}{19.21}$x – 19) = -99$\frac{2}{35}$ Tìm x Chuyên toán nhé Huhu th

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($\frac{1}{3.5}$x – 3)+($\frac{1}{5.7}$x – 5)+($\frac{1}{7.9}$x – 7)+…+($\frac{1}{19.21}$x – 19) = -99$\frac{2}{35}$
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Mary 2 tháng 2021-10-28T15:05:30+00:00 1 Answers 1 views 0

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    2021-10-28T15:07:00+00:00

    $($$\dfrac{1}{3.5}$$.x$$-3)+($$\dfrac{1}{5.7}$$.x-5)+($$\dfrac{1}{7.9}$$.x-7)+…+($$\dfrac{1}{19.21}$$.x-19)=-99$$\dfrac{2}{35}$

    $⇔$$\dfrac{x}{3}$$-$$\dfrac{x}{5}$$-3+$$\dfrac{x}{5}$$-$$\dfrac{x}{7}$$-5+$$\dfrac{x}{7}$$-$$\dfrac{x}{9}$$-7+…+$$\dfrac{x}{19}$$-$$\dfrac{x}{21}$$-19=-99$$\dfrac{2}{35}$

    $⇔$$\dfrac{x}{3}$$-$$\dfrac{x}{5}$$+$$\dfrac{x}{5}$$-$$\dfrac{x}{7}$$+$$\dfrac{x}{7}$$-$$\dfrac{x}{9}$$+…+$$\dfrac{x}{19}$$-$$\dfrac{x}{21}$$-3-5-7-…-19=-99$ $\dfrac{2}{35}$

    $⇔$$\dfrac{x}{3}$$-$$\dfrac{x}{21}$$-99=-99+$$\dfrac{2}{35}$

    $⇔$$\dfrac{7x}{21}$ $-$ $\dfrac{x}{21}$$=$$\dfrac{2}{35}$

    $⇔$$\dfrac{6x}{21}$$=$$\dfrac{2}{35}$

    $⇔$$x=$$\dfrac{21.2}{6.35}$$=$ $\dfrac{1}{5}$

    $\text{Mệt bở hơi tai}$

     

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