How do you write the equation of a circle if you know it's radius and the coordinates of its center

You can find the constant of proportionality by finding the ratio of

The area of square garden is 300m squared. how long is the diagonal?

The sum of the first eight terms of an arithmetic progression is 9m + 14. the fifth term of the06 progression is 2m - 6, where m is a constant.given that the first term of the progression is 26,find the value of the common difference, d and thevalue of m.