ElectricPavlov

Here is a graph to help you check your answers.......

https://www.desmos.com/calculator/npmqp38gfq

Here is a very similar question with slghtly different numbers.....do you think you can use the methodology to solve THIS problem?

At least TRY:

https://web2.0calc.com/questions/circle-question-precalculus

period = 8 seconds          freq = 1/8      1/8 x 2pi  = pi /4

    amplitude = 7

7 sin ( pi/4 x)     

Graph:

https://www.desmos.com/calculator/k5zytneicn

Complete the square for x and y

(x-3.5)^2      +   (y+ 4.5)^2   = 1   +  12.25   + 20.25    <===========  red part is  r²

center =   (3.5 , -4.5)  

x ( .04)     + (15 000 - x) (.05)    = 690       solve for x  (the amount at 4%)     then the 5% amount is 15 000 - x

If you must have two variables

x = 4% amount

y = 5% amount  

x + y = 15000            y =   (15000 - x)

.04 x   +  .05 y = 690             now  y = 15 000 - x    sub that in

.04x   + .05 ( 15000 - x) = 690

3n   = money fron 'n' raffle tix

3n  > =.07n  + 45

n >= 15.35                              they must sell at least 16 tix to make money

(10²⁰)² - 2·10²⁰ + (-1)²                    Slight correction ......

10⁴⁰ - 2 * 10²⁰  +1  

Smallest integer > sqrt (690)                   sqrt 690 = 26.3

Smallest integer > sqrt 690  is then 27

Not sure what you mean by this part : 690−−√690

         690 -   - sqrt 690

          = 690 + sqrt 690

           =   690  + 26.3   = 716.3               then the answer would be   717   

If 64 cm is the circumference of A     then B AREA = 64/4 = 16 cm²

Area =   pi * r^2

     16               =   pi  r^2

     16 / pi =    r^2 

          r  = 2.2568 cm