Answer:
All real numbers
Step-by-step explanation:
21 - 7x = 7(3 - x)
21 - 7x = 21 - 7x
Since both sides of the equation are equal, the answer is all real numbers.
Step-by-step explanation:
12. n^2+2n
if you insert 1 for k and then work up by inserting 2 for k and adding those together and stoping at n.
13. 8-2(2^n)
if you insert 3 for k and then work up by inserting 4 for k and adding those together and keep on going but stopping at n.
Hope that helps :)
Answer: 
Step-by-step explanation:
You need to remember the mulplication of signs:

Knowing this, you can distributive the negative sign. Then you get:

Now you need to add the like terms. Then:

Finally, you can order the polynomial obtained in descending order. Therefore, the answer is:
