Solved on Dec 14, 2023

Find xx and yy given xy=144xy=144, x+y=30x+y=30, and xyx \geq y. What is the value of xyx-y?

STEP 1

Assumptions
1. The product of xx and yy is 144, i.e., xy=144xy = 144.
2. The sum of xx and yy is 30, i.e., x+y=30x + y = 30.
3. xx is greater than or equal to yy, i.e., xyx \geq y.
4. We need to find the value of xyx - y.

STEP 2

We have a system of two equations with two variables:
\begin{align*} xy &= 144 \\ x + y &= 30 \end{align*}

STEP 3

We can express yy in terms of xx using the second equation:
y=30xy = 30 - x

STEP 4

Substitute the expression for yy from STEP_3 into the first equation:
x(30x)=144x(30 - x) = 144

STEP 5

Expand the equation and move all terms to one side to form a quadratic equation:
x230x+144=0x^2 - 30x + 144 = 0

STEP 6

Factor the quadratic equation:
(x12)(x18)=0(x - 12)(x - 18) = 0

STEP 7

Set each factor equal to zero and solve for xx:
x12=0orx18=0x - 12 = 0 \quad \text{or} \quad x - 18 = 0

STEP 8

Solve for xx in each equation:
x=12orx=18x = 12 \quad \text{or} \quad x = 18

STEP 9

Since xyx \geq y, and both xx and yy are positive, we choose the larger value for xx:
x=18x = 18

STEP 10

Now, substitute x=18x = 18 into the second equation to find yy:
18+y=3018 + y = 30

STEP 11

Solve for yy:
y=3018y = 30 - 18

STEP 12

Calculate the value of yy:
y=12y = 12

STEP 13

Now that we have both xx and yy, we can find the value of xyx - y:
xy=1812x - y = 18 - 12

STEP 14

Calculate the difference:
xy=6x - y = 6
The value of xyx - y is 6.

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