Why is the middle term 2ab in (a+b)^2 and -2ab in (a-b)^2 when written in standard form

An alien has just landed from the planet, iksnimak. he would like to leam how to add two fractions when thedenominators are the same. write a paragraph that explains to our alien friend, in your own words, the detailsabout how to add the fractions, how to change the result to a mixed number, and how to reduce the fractionpart. use this problem as your example: the two fractions are 5/8 & 7/8

The variable z is directly proportional to x, and inversely proportional to y. when x is 4 and y is 13, z has the value 1.2307692307692. what is the value of z when x= 9, and y= 20

Aquantity with an initial value of 3900 decays exponentially at a rate of 35% every hour. what is the value of the quantity after 0.5 days, to the nearest hundredth?