Question

Please answer quickly! 50 POINTS! Brainliest!
A biologist created the following graph to show the relationship between the temperature of water (x), in degrees Celsius, and the number of insect larvae (y) in the water:

graph of y equals minus 2 times the square of x plus 20 times x plus 400

What do the x-intercepts of the graph represent? (5 points)
The water had no larvae at −10 degrees Celsius and 20 degrees Celsius.
There were 20 larvae in the water at 0 degrees Celsius.
The water had maximum larvae at −10 degrees Celsius and 20 degrees Celsius.
There were 10 larvae in the water at 0 degrees Celsius.

Answer 1

Answer:

The water had no larvae at −10 degrees Celsius and 20 degrees Celsius.

Step-by-step explanation:

We are given the function, $y = -2x^{2} + 20x + 400$

where

x = temperature of water (in degrees)

y = number of insect larvae in water

What do the x-intercepts of the graph represent?

The x - intercept is when y = 0, and y is the number of insect larvae in the water. So this means there is NO insect larvae in the water.

$y = -2x^{2} + 20x + 400\\0 = -2x^{2} + 20x + 400\\quadratic \ formula:\\\frac{-20 + \sqrt{20x^{2} -4(-2)(400)}}{2(-2)} \\\frac{-20 +\- 60}{-4} \\\frac{-20 + 60}{-4} = -10\\\frac{-20 - 60}{-4} = 20$

Hence, when there was no larvae in the water, the water temperature was 20 and -10