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What is the sum of two numbers is 9 and their product is 20. Find the two numbers

**Comments**

The two numbers are 4 and 5

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x + y = 9 ------------ equation 1

x*y = 20 ----------- equation 2

From equation 1,

x = 9 - y ---------- equation 3

Substituting into equation 2

(9 - y)y = 20

9y - y^{2} = 20

y^{2} -9y + 20= 0

(y^{2} -5y) - (4y + 20) = 0

y(y - 5) - 4(y - 5) = 0

y = 5 or y = 4

If y = 5,

Substitute y = 5 in equation 3

x = 9 - 5

x = 4

If y = 4,

substitute y = 4 in equation 3

x = 9 - 4

x = 5

There fore,

x = 5, y = 4

OR

x = 4, y = 5

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