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Thought-Process to Discover Knowledge

Welcome to nubtrek.

Books and other education websites provide "matter-of-fact" knowledge. Instead, nubtrek provides a thought-process to discover knowledge.

In each of the topic, the outline of the thought-process, for that topic, is provided for learners and educators.

Read in the blogs more about the unique learning experience at nubtrek.continue

In this lesson, identities are explained in general.

 •  identity is a statement of one expression modified as per PEMA / CADI properties to arrive at a different expression.

 •  These two expressions are identical.

 •  And, identities are studied because one form of identity can be modified into its equivalent form for some purpose.

It is very important to go through this once to understand in-equalities in algebra.

click on the content to continue..

What does 'identity' mean?

  • It is just a name.
  • equality of two expressions; left and right hand side are identical
  • equality of two expressions; left and right hand side are identical

Answer is 'equality of two expressions; left and right hand side are identical'

Identities are statements that specify two expressions as equal.

In numerical terms, some examples of the identities are
 •  `5xx(2+3) = 5xx2+5xx3`
(left hand side equals to right hand side )
 •  `4-0 = 4`
(left hand side and right hand side are equal.)

Similar to identities of numerical expressions, algebraic identities are statements that specify two algebraic expressions as equal.
(left hand side equals right hand side)
 •  `a^2+2a^2+b = 3a^2+b`
 •  `(2+x)x = x^2+2x`

Consider the expression `(2 + 3) xx (1 + 5)`. Which of the following equals the given expression?

  • `= 2xx1 + 3xx1 + 2xx5 + 3xx5`
  • `= 2xx1 + 3xx1 + 2xx5 + 3xx5`
  • `=2 + 3xx1 + 5`

The answer is "`= 2xx1 + 3xx1 + 2xx5 + 3xx5`"

`color(coral)((2 + 3))xx color(deepskyblue)((1 + 5))`

`2+3` is a number by closure property and by distributive property it is distributed over addition
`=color(coral)((2 + 3))xx color(deepskyblue)((1))` + `color(coral)((2 + 3))xx color(deepskyblue)((5))`

by distributive property `=color(coral)((2))xx color(deepskyblue)((1))` + `color(coral)((3))xx color(deepskyblue)((1))`

`=color(coral)((2))xx color(deepskyblue)((5))` + `color(coral)((3))xx color(deepskyblue)((5))`

This proves that for any number `p, q, b, c` the following is true. `color(coral)((p+q))xx color(deepskyblue)((b+c))`
`= color(coral)(p) color(deepskyblue)(b) + color(coral)(q)color(deepskyblue)(b) + color(coral)(p) color(deepskyblue)(c) + color(coral)(q)color(deepskyblue)(c)`

The left hand side might be complex to compute, wherein the right hand side is easier to compute. For example `98 xx 98` involves large values to multiply and add. The same in `100xx100 -100xx2-100xx2+2xx2` is simpler.

Algebraic identities are equations of two expressions wherein one expression is modified per PEMA precedence / CADI Laws and Properties of Arithmetics to derive the other equivalent expression.

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