Class 8    Math    Algebraic Expressions
Problem Based on Algebraic Expressions and Identity

Question: Find multiplication of 198 and 202 using the identity (x+a)(x+b) = x2 + (a+b)x + ab

Answer: In this question, we need to multiply two numbers 198 and 202 by using the standard formulas given in the question.

Let us see how we solve this question. First we need to rewrite the numbers 198 and 202 in such a way that it takes the form of (x+a)(x+b). So, 198 can be written as 200 − 2 or 200 + (-2) and 202 can be written as 200 + 2.

Let us place these values in the formula format. We need to multiply following numbers:

     (200 + (−2)) (200 + 2)

In this case x is 200, a is −2, and b is +2. Let us put all together in the equation:

     (200 + (-2)) (200 + 2)
     = 2002 + ((−2) + 2)200 + (−2)(2)
     = 40000 + 0 − 4
     = 39996

Keep on practicing these types of questions, try changing the number, see the different ways to solve one problems and this will improve your thinking and analyzing skills. As always, please feel free to reach out to us by clicking on the 'contact' link appears at top of the each page of this website.