If x-y = 4 and xy = 21 then find the value of x 3 - y 3
Answers
Answered by
21
by looking at the equations u will get x= 7 and y = 3
then x³= 343
y³ = 27
343-27 = 316
or if u don't get the values of x and y In ur head.
try this it will help
x-y=4
(x-y)² = 16
x²+y²- 2(xy)= 16
x²+y²- 42 = 16
x²+y²= 58
x³-y³= ( x-y) ( x²+y²+xy)
x³-y³= 4(58+21)
x³-y³=316
then x³= 343
y³ = 27
343-27 = 316
or if u don't get the values of x and y In ur head.
try this it will help
x-y=4
(x-y)² = 16
x²+y²- 2(xy)= 16
x²+y²- 42 = 16
x²+y²= 58
x³-y³= ( x-y) ( x²+y²+xy)
x³-y³= 4(58+21)
x³-y³=316
Anonymous:
good :))
Answered by
3
After we solve the given equation...... we will get the value of y as 3 and x as 7......
So now to find...x³-y³
7³-3³=7×7×7-3×3×3
=343-27
=316
So now to find...x³-y³
7³-3³=7×7×7-3×3×3
=343-27
=316
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