Question 20

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Jambmaths question: 

A binary operation * is defined by a* b =ab, If  a * 2 =2 – a. Find the possible value of a

Option A: 

1, –2

Option B: 

1, 2

Option C: 

2, –2

Option D: 

1, –1

Jamb Maths Solution: 

$\begin{align}  & a*2={{a}^{2}}-----(i) \\ & a*2=2-a----(ii) \\ & {{a}^{2}}=2-a \\ & {{a}^{2}}+a-2=0 \\ & (a+2)(a-1)=0 \\ & a=-2\text{ or }a=1 \\\end{align}$

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