Question

1/x + 1/y = 7/12 xy = 12 find x and y

Answer 1

me assume that shood be (7/12)xy=12

so xy=(12/7)*(12)=144/7=20.57142857142851...

(1/x) +(1/y)=12   become 12xy=x+y

or (x+y)=12*144/7=246.857142857...

so y=246.85714... -x

xy=x*(246.85714-x)=20.57142857...

-x^2 +246.85714x -20.57142857=0

or +x^2 -246.85714x +20.57142857=0

quadratik equashun giv zeroes...x=246.7737785 or 0.0833615

Answer 2

1/x + 1/y = 7/12 and xy = 12 therefore for xy = 12 make y subject of the formula  ; y = 12/x

Solve by elimination 1/x + 1/(12/x) = 7/12

                                 1/x + x/12 = 7/12            NB: 1/(12/x) simplified becomes x/12

                                multiply each by 12x  or use 12x as a factor

                                 (12x x 1/x) + (12x x x/12) = (12x x 7/12)

                                 12 + x^2 = 7x   Rearrange to make zero subject of the formula

                                 x^2 - 7x + 12 = 0 then factorise

                                 (x -3) (x -4) = 0

                                 (x-3) =0 and (x -4) =0

                                  x = 3 and x = 4