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$Old$ July 2nd, 2009, 04:04 AM

Sailee316 $Sailee316 is offline$

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$Default$ subtracting powers?

How do you subtract powers?

(i) 72 – 62
(ii) 92 – 82

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$Old$ July 2nd, 2009, 04:14 AM

yeongil $yeongil is offline$

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Originally Posted by Sailee316 $View Post$

How do you subtract powers?

(i) 72 – 62
(ii) 92 – 82

Thanks

These are not powers. Do you mean
$\text{(i)}\;7^2 - 6^2$ and
$\text{(ii)}\;9^2 - 8^2$ ?

If so, then just evaluate the powers separately and then subtract:
$\begin{aligned}7^2 - 6^2 &= 49 -36 \\&= 13\end{aligned}$

I'll let you try the other one yourself.

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$Old$ July 2nd, 2009, 06:17 AM

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Originally Posted by yeongil $View Post$

These are not powers. Do you mean
$\text{(i)}\;7^2 - 6^2$ and
$\text{(ii)}\;9^2 - 8^2$ ?

If so, then just evaluate the powers separately and then subtract
[snip]

Alternatively, use $a^2 - b^2 = (a - b)(a + b)$ .

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