well idk about #16 but #20 I can answer it OK look, number 20 , Y represent height X represent time OK, number a is asking for maximum height , the ball will reach the maximum height when time equal zero so Y = -16(0)^2 + 15(0) + 6 which equals 6 so maximum height is 6 feet, and as for number b , when the ball hit the ground the distance will equal zero so Y = 0 , so by factorizing. the given equation find the values of X, U will probably find 2 values one in +ve and one in -ve take the positive and neglect the -ve and we are done
