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If x varies directly as y, and x = 7.5 when y = 10, find x when y = 4

The distribution of a sample of the outside diameters of pvc pipes approximates a symmetrical, bell-shaped distribution. the arithmetic mean is 14.0 inches, and the standard deviation is 0.1 inches. about 68% of the outside diameters lie between what two amounts?

Factor the gcf out of the polynomial 9x^6+6x^4+15x^3