Formula is
ₙCₖ = (n!)/( k!*(n-k)! )
so ₇C₃ = (7!) / (3! * (7-3)!)
and 7! = 7 * 6 * 5 * 4 * 3 * 2 * 1
= (7 * 6 * 5 * 4 * 3 * 2 * 1)/(3 * 2 * 1 * 4!)
= (7 * 6 * 5 * 4)/(4!)
= (7 * 6 * 5 * 4)/(4 * 3 * 2 * 1)
= (7 * 6 * 5 )/(6 * 1)
= (7 * 5 )/( 1)
= 35
This is a problem of
Arithmetic that is a branch of mathematics that consists of the study of numbers. Its main goal is the study of the traditional operations on them just as: <em>addition, subtraction, multiplication and</em><span><em> division</em>. </span>There is an order of operation to solve problems in arithmetic that is the way you choose to simplify expressions. This order is like this:
1. First. Solve Parentheses.
2. Second. Solve Exponents (and root).
3. Third. Solve Multiplication and Division
3. Fourth. Solve addition and subtraction.
So let's apply these concepts to our problem:

We don't have parentheses, so let's apply
second step:

Applying
third step:

Finally, applying
fourth step, the result is:
Every unit of length<span> has a </span>corresponding<span> unit of area, namely the area of a </span>square<span>with the given </span>side length<span>. Thus areas can be measured in </span>square<span> metres (m</span>2<span>), </span>square<span> centimetres (</span>cm2<span>), </span>square<span> millimetres (mm</span>2<span>), </span>square<span> kilometres (km</span>2<span>), </span>square<span> feet (</span>ft2<span>), </span>square<span> yards (</span>yd2<span>), </span>square<span> miles (mi</span>2<span>), and so forth.
so, to shorten it down, its a little number 2.
</span><span>https://en.wikipedia.org/wiki/Area</span>
Answer:

Step-by-step explanation:
As this is a reflection over the y axis we are looking for a function g so that
g(-x)=f(x) for x real
it gives g(x)=f(-x)
so the correct answer is

we can write it as

you can see the graphs below
hope this helps