Express \(3x^{2} - 6x + 10\) in the form \(a(x - b)^{2} + c\), where a, b and c are integers. Hence state the minimum value of \(3x^{2} - 6x + 10\) and the ...

Assessment: WAEC SSCE - Further Mathematics - 2012 (Essay) Subject: Further Mathematics

Question 1 Report

Express \(3x^{2} - 6x + 10\) in the form \(a(x - b)^{2} + c\), where a, b and c are integers. Hence state the minimum value of \(3x^{2} - 6x + 10\) and the value of x for which it occurs.

Answer Details

Express \(3x^{2}-6x+10\) as \(a(x-b)^{2}+c\).

Factor 3 from the x-terms and complete the square:

\[3x^{2}-6x+10=3(x^{2}-2x)+10=3\big[(x-1)^{2}-1\big]+10\]\[=3(x-1)^{2}-3+10=3(x-1)^{2}+7\]

So \(a=3,\ b=1,\ c=7\).

Minimum value. Since \(3(x-1)^{2}\ge 0\) and is zero when \(x=1\), the least value of the expression is

\[3(0)+7=7\ \text{at } x=1\]

The minimum value is \(7\), occurring at \(x=1\).

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