√- 81 doesn't result in a rational number because you can't get a negative from squaring any number. Instead you get a number with an imaginary number.
13 - √- 81 = 13 - 9i
Answer: x = 20.
Step-by-step explanation:
x and (3x + 10) combine to form a right angle, shown in the diagram by the small square joining the perpendicular lines.
Right angles are 90 degrees, so you can add both angles to get 90:

Answer:
I'm also struggling with that too
Answer:
= 34.5
Step-by-step explanation:
The n th term of an arithmetic sequence is
= a₁ + (n - 1)d
where a₁ is the first term and d the common difference
Given
= 121.5, then
a₁ + (69 × 1.5) = 121.5
a₁ + 103.5 = 121.5 ( subtract 103.5 from both sides )
a₁ = 18
Hence
= 18 + (11 × 1.5) = 18 + 16.5 = 34.5