If x^2 + y^2 =58 and xy=21, find the vlaue of (x+y)^2 and (x-y)^2. if x^2+y^2=1 and xy = 7.5 , find the value of (x^4 -y^4) i really don't know how to start , have been thinking for the whole night, still can't do it Thank you.
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Originally Posted by vivien If x^2 + y^2 =58 and xy=21, find the vlaue of (x+y)^2 and (x-y)^2. get the idea? if x^2+y^2=1 and xy = 7.5 , find the value of (x^4 -y^4) i really don't know how to start , have been thinking for the whole night, still can't do it Thank you. ...
Originally Posted by vivien If x^2 + y^2 =58 and xy=21, find the vlaue of (x+y)^2 and (x-y)^2. ....(1) ....(2) From (2) you can say and sub this back into (1) giving ....(1) Now solve for x I think skeeter's way could be better.
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