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Inequality Value Of X And Y

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Subject
Mathematics
Type
Homework
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Surname: 1
Name:
Tutor’s Name:
Course:
Date:
Inequality Value of X and Y
If x²+4y²=40 and xy=6, what will be the value of x+2y? Please explain how you arrived
at your answer.
X
2
+ 4Y
2
= 40 … (1) and XY=6… (2). Make X the subject of the equation in 2.
Hence, X=6/Y(3). Substitute equation (3) in equation (1), we obtain (6/Y)
2
+ 4Y
2
=
40… (4)
Solve for Y in equation (4), 36/Y
2
+ 4Y
2
= 40. To substitute for the Y
2
in the
denominator, we multiply both sides of the equation with the value Y
2
. (36/Y
2
) *Y
2
+ (4Y
2
* Y
2
)
= (40 * Y
2
). After multiplying we get the following equation, 36 + 4Y
4
= 40Y
2
. Given that all the
values are multiples of 4, we divide all through with 4. 36/4 + 4Y
4
/4 = 40Y
2
/4 which gives us 9
+ Y
4
= 10Y
2
. Make the equation to quadratic form as in the formulae ax
2
+ bx + c = 0, which is
Y
4
- 10Y
2
+ 9 = 0. Solve the equation using the quadratic formula y=(b±b24ac)/2a.
Where a = 1, b = -10 and C = 9. Therefore, Y
2
= {-(-10) ±(-10
2
) (4*1*9)}/ (2*1)
Y
2
= {10 ±(100) (36)}/2, Y
2
= (10 ±64)/2, Y
2
= (10±8)/2, Y
2
= 2/2,18/2. Therefore,
Y
2
= 1 or 9. Square root of Y
2
we get Y = 1 or 3. Hence, Substituting Y in equation 3, we obtain
X= 6/1 (when Y = 1) and X = 6/3 (when Y = 3). So, X = 6 or 2. Hence, the values of X and Y
are; when Y = 1, X = 6, and when Y = 3, X = 2.
To obtain the value of X + 2Y, we substitute the values of X and Y in the equation.

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Surname: 1 Name: Tutor’s Name: Course: Date: Inequality Value of X and Y If x²+4y²=40 and xy=6, what will be the value of x+2y? Please explain how you arrived at your answer. X2 + 4Y2 = 40 … (1) and XY=6… (2). Make X the subject of the equation in 2. Hence, X=6/Y… (3). Substitute equation (3) in equation (1), we obtain (6/Y)2 + 4Y2 = 40… (4) Solve for Y in equation (4), 36/Y2 + 4Y2 = 40. To substitute for the Y2 in the denominator, we multiply both sides of the equation with the value Y2. (36/Y2) *Y2 + (4Y2 * Y2) = (40 * Y2). After multiplying we get the following equation, 36 + 4 ...
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