Toán Lớp 8: a,|7x-3|-2x+6=0
b,|x-15|+1-3x=0
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Toán Lớp 8: a,|7x-3|-2x+6=0
b,|x-15|+1-3x=0
Comments ( 2 )
<=>|7x-3|=2x-6
<=>\(\left[ \begin{array}{l}7x-3=2x-6\\7x-3=-(2x-6)\end{array} \right.\)
<=>\(\left[ \begin{array}{l}7x-2x=-6+3\\7x+2x=3+6\end{array} \right.\)
<=>\(\left[ \begin{array}{l}5x=-3\\9x=9\end{array} \right.\)
<=>\(\left[ \begin{array}{l}x=-3/5\\x=1\end{array} \right.\)
Vậy phương trình có 2 nghiệm S={-3/5;1}
b,|x-15|+1-3x=0
<=>|x-15|=3x-1
<=>\(\left[ \begin{array}{l}x-15=3x-1\\x-15=-(3x-1)\end{array} \right.\)
<=>\(\left[ \begin{array}{l}x-3x=-1+15\\x+3x=1+15\end{array} \right.\)
<=>\(\left[ \begin{array}{l}-2x=14\\4x=16\end{array} \right.\)
<=> \(\left[ \begin{array}{l}x=-7\\x=4\end{array} \right.\)
Vậy phương trình có tập nghiệm S={-7;4}