Answer:
B
Step-by-step explanation:
A. these simply to 21 + 7x and 21 + 3x
- this one is incorrect because the 7x and 3x are different
B. these simplify to 10 + x and 10 + x
- this is the correct one since they are exactly the same
C. these simplify to 21x and 7x + 21
- these two are not the same because one expression has only a number with a variable but the other one has a number with a variable <em>and </em>another number
D. these simplify to 
and 
- in subtraction, the order of the 3 and the x matters, so the equations are not the same
- example: 6 - 4 = 2 but 4 - 6 = -2
Answer:
The answer is -6
Step-by-step explanation:
Hope it helped you!
Answer:
343
Step-by-step explanation:
7 cubed = 7 x 7 x 7 = 343
so, 343 is a perfect cube.
The elephant that weighs 2.85 tons
Answer:
Ф = 0 and Ф = π
Step-by-step explanation:
* Lets explain how to solve the problem
∵ sin Ф + 1 = cos²Ф, where 0 ≤ Ф < 2π
- To solve we must to replace cos²Ф by 1 - sin²Ф
∵ sin²Ф + cos²Ф = 1
- By subtracting sin²Ф from both sides
∴ cos²Ф = 1 - sin²Ф
- Lets replace cos²Ф in the equation above
∴ sin Ф + 1 = 1 - sin²Ф
- Subtract 1 from both sides
∴ sin Ф = - sin²Ф
- Add sin²Ф for both sides
∴ sin²Ф + sin Ф = 0
- Take sin Ф as a common factor from both sides
∴ sin Ф(sin Ф + 1) = 0
- Equate each factor by 0
∵ sin Ф = 0
∴ Ф = 0 OR Ф = 2π
∵ sin Ф + 1 = 0
- Subtract 1 from both sides
∴ sin Ф = -1
∴ Ф = π
∵ 0 ≤ Ф < 2π
∵ Ф < 2π
∴ We will refused the answer Ф = 2π
∴ Ф = 0 and Ф = π
