Quadratic Equation

4. The sum S of first n natural numbers is given by S=n(n + 1)/n . Find n, if the sum is 351.
5. the expression b2−4ac is called the
7. is the second element in an ordered pair
8. how many terms are there in quadratic equation
11. term for non variable
15. a polynomial with only 2 terms
16. known as the "x" coordinate of a point, shown on the horizontal line,

1. A shopkeeper buys a number of books for Rs 80. If he had bought 4 more books for the same amount, each book would have cost him Re 1 less. How many books did he bought?
2. an unknown term
3. A polynomial with three unlike terms
6. U-shaped plane curve
9. polynomial, which has only one term
10. Square root of a negative number
12. in a flight of 600 Km, an aircraft was slowed down due to bad weather. Its average speed for trip was reduced by 200 Km/h and the time increased by 30 minutes. Find the duration of flight.
13. Find the value of k for which the roots of the quadratic equation (k -4)x2+2(k -4)x +2 = 0 are equal.
14. Zero are also called