Page 18 - CHAPTER 4 (Quadratic equations)

CHAPTER 4

QUADRATIC EQUATIONS

Checkpoint - 4

1. A two digit number is such that the product of its digits is 12. When

9 is added to the number, the digits interchange their places, find

the number.

2. A shopkeeper buys a number of books for Rs 80. If he had bought

4 more for the same amount, each book would have cost Rs 1 less.

How many books did he buy?

3. The sum of two numbers is 15. If the sum of their reciprocals is 3/10,

find the numbers.

4. A man bought an article for Rs x and sold it for Rs 16. If his loss was

x percent, find the cost price of the article.

Bird’s-eye view

Quadratic Equation

A polynomial equation of degree two is called quadratic equation.

General form of quadratic equation is

2
ax +bx+ c= 0, where b, c ∈ R and a≠ 0.

Roots of the Quadratic Equation

2
x= α is said to be root of the quadratic equation ax + bx + c, a≠0, if x=α

satisfies the quadratic equation i.e. a +b+c=0.
2
A quadratic equation has two roots, they be real or Imaginary.

We can determine the roots of given quadratic equation by the

quadratic formula (Sridharacharya rule) as

x= -b±√D
2a

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