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Class 9MathematicsIntroduction to PolynomialsLinear polynomialsMediumLevel 34
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If (p(x)=ax+18) and (p(-3)=0), what is the value of (a)?

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Answer and explanation

Correct answer: \(6\)

Given \(p(x)=ax+18\), substituting \(x=-3\) gives \(p(-3)=-3a+18\). Since \(p(-3)=0\), we get \(-3a+18=0\), so \(a=6\). If \(a=-6\), then \(p(-3)=36\), not zero. Exam tip: Substitute the given value of \(x\) carefully before solving for the unknown coefficient.

Related tags

PolynomialsLinear PolynomialsSubstitutionZero Of PolynomialAlgebra

Frequently asked questions

What is the correct answer to this question?

\(6\)

Why is this the correct answer?

Given \(p(x)=ax+18\), substituting \(x=-3\) gives \(p(-3)=-3a+18\). Since \(p(-3)=0\), we get \(-3a+18=0\), so \(a=6\). If \(a=-6\), then \(p(-3)=36\), not zero. Exam tip: Substitute the given value of \(x\) carefully before solving for the unknown coefficient.

Which subject and chapter does this question cover?

This is a Class 9 Mathematics question. Chapter: Introduction to Polynomials. Topic: Linear polynomials.

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10 more MCQs
  1. 1If the highest power in a polynomial is 1, what is it called?
  2. 2Which expression is not a linear polynomial?
  3. 3Which expression is a polynomial but not a linear polynomial?
  4. 4Which statement is correct about the zeroes of a non-zero linear polynomial?
  5. 5Which expression is a polynomial in (s) and has degree (1)?
  6. 6If \(p(x)=ax+b\), where \(a\ne0\), is a linear polynomial, which property of its graph is always true?
  7. 7Which of the following expressions is a linear polynomial in \(x\)?
  8. 8A taxi charges a fixed fee of ₹50 and ₹12 per kilometre. If the distance travelled is represented by \(x\), which statement about \(C(x)=12x+50\) is correct?
  9. 9What type of polynomial is (4x-9)?
  10. 10What is the degree of a linear polynomial?
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