Pretty easy geometry just pretty stuck and need help ASAP

Use the inverse of the function y=x^2-18x to find the unknown value [tex]y = \sqrt{bx + c \: + d} [/tex]

Hurry and answer this! circle x with a radius of 6 units and circle y with a radius of 2 units are shown which steps would prove the circles similar? translate the circles so they share a common center point, and dilate circle y by a scale factor of 4. translate the circles so the center of one circle rests on the edge of the other circle, and dilate circle y by a scale factor of 4. translate the circles so they share a common center point, and dilate circle y by a scale factor of 3. translate the circles so the center of one circle rests on the edge of the other circle, and dilate circle y by a scale factor of 3

Julius sold five times as many computers as sam sold last year. in total, they sold 78 computers. how many computers did julius sell?