Question

using identities find the value of (39)2

Answer 1

Hope it helps................

Answer 2

Concept

If there are two numbers a and b, then the square of their difference is given by the following formula-

(a - b)^2 = a^2 + b^2 - 2ab

Given

an expression: (39)^2

Find

we need to find the value of the given expression using algebraic identities.  

Solution

We have

(39)^2

39 can also be written as (40 - 1)

= (40 - 1)^2

now, we apply (a - b)^2 formula in the above expression

Here a = 40 and b = 1

Thus, the expression becomes,

40^2 + 1^2 - 2(40)(1)

= 1600 + 1 - 80

= 1520 + 1

= 1521

Thus, the value of (39)^2 is 1521.

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