What substitution should be used to rewrite 4x4 – 21x2 + 20 = 0 as a quadratic equation?
2 answers:
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Answer:
4x - 24
Step-by-step explanation:
Answer:
Step-by-step explanation:
x is the number of years. y is the population after x years.
Each year, the population decreases by 22%, since 100% - 22% = 78%, and 78% = 0.78, each year, the population is 0.78 of the previous year's population.
year zero: y = 300
year 1: y = 300 * 0.78 = 300 * (0.78)^1
year 2: y = (300 * 0.78) * 0.78 = 300 * (0.78)^2
year 3: y = ((300 * 0.78) * 0.78) * 0.78 = 300 * (0.78)^3
year x: y = 300(0.78)^x