Suggested Answer
900a+30b+c=6....(1)3600a+60b+c=7...(2)10000a+100b+c=4....(3)(2)-(1)2700a+30b=1.....(4)(3)-(1)9100a+70b=-2...(5) solving (4) and (5) then putting a, b into (1)a=-13/8400, b=29/168, c=31/14 The graph is like a parabola with upward dome, it's head at upside and two legs downwards.