Question
Factorise:
$21\text{x}^2-2\text{x}+\frac{1}{21}$
$21\text{x}^2-2\text{x}+\frac{1}{21}$
✓
Answer
$21\text{x}^2-2\text{x}+\frac{1}{21}$
$21\text{x}^2-\text{x}-\text{x}+\frac{1}{21}$
$=21\text{x}\Big(\text{x}-\frac{1}{21}\Big)-1\Big(\text{x}-\frac{1}{21}\Big)$
$=\Big(\text{x}-\frac{1}{21}\Big)(21\text{x}-1)$
$21\text{x}^2-\text{x}-\text{x}+\frac{1}{21}$
$=21\text{x}\Big(\text{x}-\frac{1}{21}\Big)-1\Big(\text{x}-\frac{1}{21}\Big)$
$=\Big(\text{x}-\frac{1}{21}\Big)(21\text{x}-1)$
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