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The graphs of $y=x^4$ and $y=5x^2-6+4x^2$ intersect at four points with $x$-coordinates $\pm \sqrt{m}$ and $\pm \sqrt{n}$, where $m > n$. What is $m-n$?

 Sep 1, 2023
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To find the $x$-coordinates of the points of intersection between the graphs of $y=x^4$ and $y=5x^2-6+4x^2$, we need to set the two equations equal to each other and solve for $x$. 

Setting $x^4 = 5x^2-6+4x^2$, we can combine like terms to obtain $x^4 - 9x^2 + 6 = 0$. This is a quadratic equation in terms of $x^2$, so we can use the quadratic formula to solve for $x^2$:

x2=(9)±(9)24(1)(6)2(1)

Simplifying further, we have:

x2=9±81242
x2=9±572

Since we are only interested in real solutions, we can discard the negative square root. Thus, we have:

x2=9+572

To find the values of $m$ and $n$, we need to determine which value is greater. Let's denote $\sqrt{m}$ as the larger solution and $\sqrt{n}$ as the smaller solution. Therefore, we have:

m=9+572
n=9572

To simplify these expressions, we can rationalize the denominators by multiplying both the numerator and denominator by the conjugate of the denominator. This gives us:

m=9+57222
n=957222

Simplifying further, we have:

m=(9+57)22
n=(957)22

Now, let's simplify the expressions under the square roots:

(9+57)2=18+257
(957)2=18257

Therefore, we have:

m=18+2572
n=182572

To determine the value of $m-n$, we need to subtract $\sqrt{n}$ from $\sqrt{m}$:

mn=(18+2572)2(182572)2

Expanding and simplifying, we have:

mn=(18+257)2(18257)2
mn=2572
mn=57

Therefore, the value of $m-n$ is $\sqrt{57}$.

 

 Sep 2, 2023
edited by Guest  Sep 2, 2023

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