If x+y=8 and xy =15,find the value of x-y?
Answers
Answered by
15
Given,
x+y=8,
xy=15.
x-y=?
we know that, (a-b)² = (a+b)²-4ab
(x-y)²=(x+y)²-4xy
=8²-4(15)
=64-60
=4
(x-y)²=4
x-y=√4
=2
x+y=8,
xy=15.
x-y=?
we know that, (a-b)² = (a+b)²-4ab
(x-y)²=(x+y)²-4xy
=8²-4(15)
=64-60
=4
(x-y)²=4
x-y=√4
=2
mdtauqeer:
why the square root in last line
???
Because (x-y)^2=(x-y)*(x-y) and 4= 2*2 or -2*-2 hence there will be two answers +2&-2
if a^2 = 4 then a = + or - root 4 = + or - 2
2 or -2 satisfies a^2 = 4
Answered by
4
x+y =8 ----(1)
xy = 15 ---(2)
(x-y) ² = (x+y)² -4xy
= 8² - 4* 15
= 64 -60
=4
(x-y) = + or - √4
= 2 or -2
xy = 15 ---(2)
(x-y) ² = (x+y)² -4xy
= 8² - 4* 15
= 64 -60
=4
(x-y) = + or - √4
= 2 or -2
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