Mathematics: A student bought some music CDs and some DVDs. The CDs cost $9 each and the DVDs $17each. He bought 7 items in all for $87

A student bought some music CDs and some DVDs. The - id10062285, catherinethomas0826

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18.01.2021

$k=-\frac{2}{7}$

Step-by-step explanation:

The two equations given represent two straight lines in 2-D graph.

The two lines will not intersect if they are parallel.

Hence the two equations will not have solution if the lines are parallel and not coincident.

The condition for 2 lines given by the equations :

ax+by+c=0

dx+ey+f=0 to be parallel but not coincident is:

$\frac{a}{d}=\frac{b}{e}\neq\frac{c}{f}$

here a=2 b=-3k c=-1 d=4 e=k+2 f=-5

$\frac{2}{4}=\frac{-3k}{k+2}\\k+2=-6k\\k=-\frac{2}{7}$

But also:

$\frac{-3k}{k+2}\neq\frac{1}{5}$

Hence the value of k is -2/7.

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