How this exponent expression is reduced

[Sabeel]

Initially the expression A has 8 terms. So how is it reduced in the second line to 5 terms?
Could you show me, please?
Thank you.
\begin{align*}
A&=10^{28} -10^{22} +61\times10^{14}+12\times10^{21}-12\times10^{15}+3\times10^{9}-36\times10^{8}+9\times10^{2}\\
&=10^{28} +2\times10^{21}-59\times10^{14}-60\times10^{7}+9\times10^{2}
\end{align*}

 

[Opalg]

Initially the expression A has 8 terms. So how is it reduced in the second line to 5 terms?
Could you show me, please?
Thank you.
\begin{align*}
A&=10^{28} -10^{22} +61\times10^{14}+12\times10^{21}-12\times10^{15}+3\times10^{9}-36\times10^{8}+9\times10^{2}\\
&=10^{28} +2\times10^{21}-59\times10^{14}-60\times10^{7}+9\times10^{2}
\end{align*}

Hi Sabeel, and welcome to MHB!

Here's a clue that might get you started. One of the terms in the first line is $-10^{22}$. You could write that as $-10\times 10^{21}$.

 

[Sabeel]

Hi Sabeel, and welcome to MHB!

Here's a clue that might get you started. One of the terms in the first line is $-10^{22}$. You could write that as $-10\times 10^{21}$.

Thank you for welcoming me, and thank you for your answer.
Your hint is useful: $12^{21} - 10^{22} = 12^{21} -10\times 10^{21} =(12-10)10^{21}=2\times10^{21}$
I'll struggle with the others and report back.

 

[Sabeel]

$-12\times10^{15}+61\times10^{14}=-12\times10\times10^{14}=10^{14}(-120+61)=-59\times10^{14}$
$3\times10^{9}-36\times10^{8}=3\times10\times10^{8}-36\times10^{8}=10^8 (30-36)=-6\times10^{8}=-60\times10^{7}$

Your hint was more than useful. Thank you so much.