Circles

In the figure,a straight line L with slope m,passes through a point P(-2,-2) and cuts a circle C at two points Q and R.The equation of the circle C is x^2+y^2-14x-10y+49=0 and the length of QR is 8 units
(a)Find,in terms of m,the equation of the line L
(b)By considering the shortest distance from the centr of the circle C to L,find the possible vslue(s) of m

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