Evaluate
\left(9x-y\right)\left(9y-x\right)
Expand
-9x^{2}+82xy-9y^{2}
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16\left(x^{2}+2xy+y^{2}\right)-25\left(x-y\right)^{2}
Use binomial theorem \left(a+b\right)^{2}=a^{2}+2ab+b^{2} to expand \left(x+y\right)^{2}.
16x^{2}+32xy+16y^{2}-25\left(x-y\right)^{2}
Use the distributive property to multiply 16 by x^{2}+2xy+y^{2}.
16x^{2}+32xy+16y^{2}-25\left(x^{2}-2xy+y^{2}\right)
Use binomial theorem \left(a-b\right)^{2}=a^{2}-2ab+b^{2} to expand \left(x-y\right)^{2}.
16x^{2}+32xy+16y^{2}-25x^{2}+50xy-25y^{2}
Use the distributive property to multiply -25 by x^{2}-2xy+y^{2}.
-9x^{2}+32xy+16y^{2}+50xy-25y^{2}
Combine 16x^{2} and -25x^{2} to get -9x^{2}.
-9x^{2}+82xy+16y^{2}-25y^{2}
Combine 32xy and 50xy to get 82xy.
-9x^{2}+82xy-9y^{2}
Combine 16y^{2} and -25y^{2} to get -9y^{2}.
16\left(x^{2}+2xy+y^{2}\right)-25\left(x-y\right)^{2}
Use binomial theorem \left(a+b\right)^{2}=a^{2}+2ab+b^{2} to expand \left(x+y\right)^{2}.
16x^{2}+32xy+16y^{2}-25\left(x-y\right)^{2}
Use the distributive property to multiply 16 by x^{2}+2xy+y^{2}.
16x^{2}+32xy+16y^{2}-25\left(x^{2}-2xy+y^{2}\right)
Use binomial theorem \left(a-b\right)^{2}=a^{2}-2ab+b^{2} to expand \left(x-y\right)^{2}.
16x^{2}+32xy+16y^{2}-25x^{2}+50xy-25y^{2}
Use the distributive property to multiply -25 by x^{2}-2xy+y^{2}.
-9x^{2}+32xy+16y^{2}+50xy-25y^{2}
Combine 16x^{2} and -25x^{2} to get -9x^{2}.
-9x^{2}+82xy+16y^{2}-25y^{2}
Combine 32xy and 50xy to get 82xy.
-9x^{2}+82xy-9y^{2}
Combine 16y^{2} and -25y^{2} to get -9y^{2}.
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\left. \begin{cases} { 8x+2y = 46 } \\ { 7x+3y = 47 } \end{cases} \right.
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\frac { d } { d x } \frac { ( 3 x ^ { 2 } - 2 ) } { ( x - 5 ) }
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Limits
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