Question
Write the lowestrationalising factor of$ :15 - 3\sqrt2$
✓
Answer
$15-3 \sqrt{ 2} $
$15-3 \sqrt{2} =3(5-\sqrt{ 2} )$
$ =3(5-\sqrt{2 } )(5+\sqrt{ 2} )$
$ =3 \times\left[5^2-(\sqrt{2})^2\right]$
$ =3 \times[25-2]$
$ =3 \times 23$
$ =69$
Its lowest rationalizing factor is $5+\sqrt{ 2} $.
$15-3 \sqrt{2} =3(5-\sqrt{ 2} )$
$ =3(5-\sqrt{2 } )(5+\sqrt{ 2} )$
$ =3 \times\left[5^2-(\sqrt{2})^2\right]$
$ =3 \times[25-2]$
$ =3 \times 23$
$ =69$
Its lowest rationalizing factor is $5+\sqrt{ 2} $.
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