Toán Lớp 7: | x – 3 | + | x – 5 | – | x + 9 | = 10
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Toán Lớp 7: | x – 3 | + | x – 5 | – | x + 9 | = 10
Comments ( 1 )
abs(x – 3) + abs(x – 5) – abs(x + 9) = 10
⇒abs(x – 5) + abs(x – 3) = abs(x + 9) + 10
⇒x + 19 = abs(x – 5) + abs(x – 3)
⇒sqrt((x – 5)^2) + sqrt((x – 3)^2) – sqrt((x + 9)^2) = 10
$⇒40\sqrt{x^2+18x+81}\left(-x^2+34x+147\right)=3x^4+4x^3-886x^2-18156x-53109$
$⇒x=-1,\:x=3,\:x=7,\:x=-17,\:x=-21,\:x=-\frac{11}{3},\:x=27$
$⇒x<-9,\:\space-9\le \:x<3,\:\space3\le \:x<5,\:\ge \:5$
\(⇒\left[ \begin{array}{l}x=-\dfrac{11}{3}\\x=27\end{array} \right.\)