If 9x^2 + 25y^2 = 181 and xy = - 6, find the value of 3x + 5y.
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Answered by
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9 x^2 + 25 y^2 = 181 --------------------------------------- equation 1
xy = -6 -------------------------------------------- equation 2
By multiplying 30 in equation 2,
30 xy = - 180 ------------------- equation 3
Now by adding equation 1 and equation 3,
9 x^2 + 25 y^2 + 30 xy = 181 - 180
9 x^2 + 25 y^2 + 30 xy = 1
( 3 x )^2 + ( 5 y )^2 + 2 * 3 x * 5 y = 1
( 3 x + 5 y ) ^ 2 = 1
( 3 x + 5 y ) = √1
( 3 x + 5 y ) = +1 or -1.
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9 x^2 + 25 y^2 = 181 --------------------------------------- equation 1
xy = -6 -------------------------------------------- equation 2
By multiplying 30 in equation 2,
30 xy = - 180 ------------------- equation 3
Now by adding equation 1 and equation 3,
9 x^2 + 25 y^2 + 30 xy = 181 - 180
9 x^2 + 25 y^2 + 30 xy = 1
( 3 x )^2 + ( 5 y )^2 + 2 * 3 x * 5 y = 1
( 3 x + 5 y ) ^ 2 = 1
( 3 x + 5 y ) = √1
( 3 x + 5 y ) = +1 or -1.
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Anonymous:
Plz.. mark as brainliest
Why did we multiply with 30?
So that we can convert that in the form of ( 3 x + 5 y ) ^2
Can we multiply it with any other number too?
no, if we shall multiply it with any another number then it won't form 2 * 3 x * 5y
But in another question you can do that
Okay, I got it.
Thanks
Sis, plz.. mark as brainliest
Thanks sis
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