Question

Find the LCD of Number 21 and 23.

Answer 1

The LCD is basically the LCM of the denoenator so

to find LCM of exg 6 and 21, find factors and group
6=2 and 3 (one 2 and one 3)
21=3 and 7 (one 3 and one 7)
lcm=2 and 3 and 7 (include 6 and 21 in the number) (one 2 and one 3 and one 7)

LCM≈LCD
so
17.
denomenators are 2 and x^2
2=2
x^2=x times x
lcm=2 times x times x=2x^2


18.
denomenators are 6 and 9
6=2 and 3
9=3 and 3
LCM=2 times 3 times 3=18

19.
denomenators are z and 7z
z=z
7z=7 and z
lcm=7 times z=7z


20. 
denomenators are 5b and 7b^3c
5b=5 and b
7b^3c=7 times b times b times b times c
LCM=7 times 5 times b times b times b times c=7b^3c=7cb^3

21. denomenator=5 and x+2
5=5
x+2=x+2
LCM=5 times (x+2)=5(x+2)=5x+10


22. denomenators are ab and b^2c
ab=a time b
b^2c=b times b times c
LCM=a times b times b times c=ab^2c=acb^2

23. demonenators are m+n and m-n

m+n=m+n
m-n=m-n
LCM=(m+n)(m-n)=m^2-n^2


24.denoenators are k and k^2-2

k=k
k^2-2=k^2-2
LCM=k times (k^2-2)=k^3-2k

Answer 2

17. 2x²
18. 18
19. 7z²
20. 35b⁴c
21. 5x + 10
22. ab³c
23. m² - n²
24. k³ - 2k