a,7x.(x-100)=0
7x²-700=0
7x² =0+700
7x² =700
x² =700:7
x² =100
x² =50²
⇒x=50
b)17.(3x-6).(2x-8)=0
⇒\(\left[ \begin{array}{l}3x-6=0\\2x-8=0\end{array} \right.\)
⇒\(\left[ \begin{array}{l}3x=6\\2x=8\end{array} \right.\)
⇒\(\left[ \begin{array}{l}x=2\\x=4\end{array} \right.\)
⇒x∈{34;68}
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