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Subjects
Mathematics CBSE
Class 9 New
Exploring Algebraic Identities
Textbook Based Questions
13.
TBQ - Find the value of the expression - I
Exercise condition:
5
m.
Find the value of \(x^3 + y^3 - 21xy + 343\), when \(x + y = -7\).
Ans
:
\((x + y)^3 =\)
Value of \(x^3 + y^3 - 21xy + 343\) \(=\)
Identity used to solve \(=\)
(x - y)³ = x³ - 3x²y + 3xy² - y³
x³ - y³ = (x - y) (x² + xy + y²)
(x + y)³ = x³ + 3x²y + 3xy² + y³
x³ + y³ = (x + y) (x² + xy + y²)
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