Answer:

And replacing we got:

And then the final term would be:

Step-by-step explanation:
For this case we have the following expression:

And we can use the binomial theorem given by:

And for this case we want to find the fourth term and using the formula we have:

And replacing we got:

And then the final term would be:

Step-by-step explanation:
<em>2</em><em>+</em><em>1</em><em>9</em><em>=</em><em>7x</em>
<em>2</em><em>1</em><em>=</em><em>7x</em>
<em>21</em><em>÷</em><em>7</em><em>=</em><em>7x</em><em>÷</em><em>7</em>
<em>3</em><em>=</em><em>x</em>
<em>.</em><em>.</em>
Formula for perimeter a+b+a+b
12+5+12+5= 17+17= 34 .34=P