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Class 9MathematicsExploring Algebraic IdentitiesQuadratic expressionsHard
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If (9x^2+kx+25) is a perfect square and (k) is negative, what is (k)?

Answer and explanation

Correct answer: (-30)

(9x^2=(3x)^2), (25=5^2), so the middle term is (-2\cdot3x\cdot5=-30x). In exams follow the given sign.

Related tags

Quadratic ExpressionsPerfect SquareUnknown CoefficientExploring Algebraic IdentitiesMathematicsClass 9 Mcq
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  2. 2What will be the factorised form of (r^2-2rs+s^2)?
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  5. 5Which expression is a quadratic expression?
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  10. 10Which of the following quadratic expressions can be factorised using the identity for the difference of two squares?
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