How to find the derivative 5x²-2x+1

With this question! what is process of elimination? ? p.s. my brothers acc got banned so add his new one @ yamauchiyamyam17

Can someone me and do the problem plz so i can understand it more better

The length of a shadow of the building is 36m. the length of the pole, which is perpendicular to the ground, is 1.9m. the length of the pole's shadow is 1.52m. what is the height of the building?