Make an equation and solve x? (Quadratic Equations)
a stone is thrown vertically upwards from the ground. The height of the stone reaches in #t# seconds, given by #y=30t-5t^2# .
a) How long does it take for the stone to reach the ground again?
b) How long does it take for the stone to reach a height of 25 metres?
a stone is thrown vertically upwards from the ground. The height of the stone reaches in
a) How long does it take for the stone to reach the ground again?
b) How long does it take for the stone to reach a height of 25 metres?
1 Answer
a) the stone reaches the ground again at
b) the stone reaches
Explanation:
First, we assume that the ground is at
This shows us that there are two solutions to
Part b) asks us to solve for
This time we will use the quadratic formula so we need to put the equation into standard form:
Graphing the equation we see that the curve does cross
graph{30x-5x^2 [-1, 7, -3, 50]}