Find x-y if x+y=11 and xy=18

Question

it is a question from the the chapter Algebraic expressions

Answer 1

Hi Naman, given, x + y = 11 and xy = 18.

 

Step 1, solve for x in x + y = 11:

 

x + y = 11

 

x = 11 - y

 

Step 2, substitute for x in xy = 18:

 

(11 - y) * y = 18

 

11y - y² = 18

 

y² - 11y + 18 = 0

 

(y - 9) * (y - 2) = 0

 

y - 9 = 0

 

y = 9

 

and 

 

y - 2 = 0

 

y = 2

 

Step 3, find x:

 

If y = 9, then x + 9 = 11, and x = 2

 

if y = 2, then x + 2 = 11, and x = 9.

 

Answer:

 

When x = 2, y = 9.

 

When x = 9, y = 2.

 

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