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Algebraic Techniques, SM-Bank 043

Evaluate the expression  \(-2x^2\)  when:

  1. \(x=1\)  (1 mark)

  2. \(x=-2\)  (2 marks)

  3. \(x=-\dfrac{1}{2}\)  (2 marks)

Show Answers Only

a.    \(-2\)

b.    \(-8\)

c.    \(-\dfrac{1}{2}\)

Show Worked Solution
a.    \(-2x^2\) \(=-2\times 1^2\)
    \(=-2\times 1\times 1\)
    \(=-2\)

 

b.    \(-2x^2\) \(=-2\times (-2)^2\)
    \(=-2\times (-2)\times (-2)\)
    \(=-8\)

 

c.    \(-2x^2\) \(=-2\times \bigg(-\dfrac{1}{2}\bigg)^2\)
    \(=-2\times \bigg(-\dfrac{1}{2}\bigg) \times \bigg(-\dfrac{1}{2}\bigg)\)
    \(=-2\times\dfrac{1}{4}\)
    \(=-\dfrac{1}{2}\)