Question 5: what is the radius of the circle with general form x2+y2-4y=21?
question 5 options:
√21
4.58
5
25

r=5 units

Step-by-step explanation:

we have

Convert the equation of the circle in standard form

Complete the square twice. Remember to balance the equation by adding the same constants to each side

Rewrite as perfect squares

center (0,2)

radius r=5 units

d

step-by-step explanation:

the solution of the equation is 2.23 ⇒ answer b

step-by-step explanation:

* lets revise the meaning of exponential function

- the form of the exponential function is y = ab^x, where a ≠ 0, b > 0 ,  

  b ≠ 1, and x is any real number

- it has a constant base b

- it has a variable exponent x

- to solve an exponential equation, take the log or ln of both sides,  

  and solve for the variable

* lets solve the problem

∵

- the base is 7 and the exponent is x

- insert ㏑ in both sides

∴

- use the rule

∴ x ㏑(7) = ㏑(77)

- to find x divide both sides by ㏑(7)

∴

* the solution of the equation is 2.23 to the nearest 2 decimal places