Given that the number of bridges has been modeled by the function: <span>y=149(x+1.5)^2+489,505 To find the year in which, y=505000 we shall proceed as follows: From: </span>y=149(x+1.5)^2+489,505 substituting y=505000 we shall have: 505000=149(x+1.5)^2+489,505 simplifying the above we get: 0=149(x+1.5)^2-15495 expanding the above we get: 0=149x^2+447x+335.25-15495 simplifying 0=149x^2+447x-15159.8 solving the quadratic equation by quadratic formula we get: x~8.69771 or x~-11.6977 hence we take positve number: x~8.69771~8.7 years~9 years thus the year in which the number will be 505000 will be: 2000+9=2009
In the equation: , since a perfect square with the unknown "y" is isolated on the left of the equal sign, we start by applying the square root on both sides of the equality, and then on isolating the unknown:
