We need to solve for $x$ in the equation $(\frac{1}{3})^{\frac{x^2-2x}{16-2x^2}} = 4^x \sqrt{9}$.

AlgebraExponentsLogarithmsEquationsAlgebraic Manipulation
2025/3/15

1. Problem Description

We need to solve for xx in the equation (13)x22x162x2=4x9(\frac{1}{3})^{\frac{x^2-2x}{16-2x^2}} = 4^x \sqrt{9}.

2. Solution Steps

First, rewrite the equation. Since 13=31\frac{1}{3} = 3^{-1} and 9=3\sqrt{9} = 3, we have:
(31)x22x162x2=4x3(3^{-1})^{\frac{x^2-2x}{16-2x^2}} = 4^x \cdot 3
3x2+2x162x2=4x313^{\frac{-x^2+2x}{16-2x^2}} = 4^x \cdot 3^1
3x2+2x162x2=(22)x313^{\frac{-x^2+2x}{16-2x^2}} = (2^2)^x \cdot 3^1
3x2+2x162x2=22x313^{\frac{-x^2+2x}{16-2x^2}} = 2^{2x} \cdot 3^1
Taking the logarithm base 3 on both sides is not helpful because of the term 22x2^{2x}.
Let's try rewriting the original equation as follows:
(13)x22x162x2=4x9(\frac{1}{3})^{\frac{x^2-2x}{16-2x^2}} = 4^x \cdot \sqrt{9}
(13)x22x162x2=4x3(\frac{1}{3})^{\frac{x^2-2x}{16-2x^2}} = 4^x \cdot 3
Rewrite the equation by taking logarithms with base 10 on both sides:
log((13)x22x162x2)=log(4x3)\log((\frac{1}{3})^{\frac{x^2-2x}{16-2x^2}}) = \log(4^x \cdot 3)
x22x162x2log(13)=log(4x)+log(3)\frac{x^2-2x}{16-2x^2} \log(\frac{1}{3}) = \log(4^x) + \log(3)
x22x162x2log(31)=xlog(4)+log(3)\frac{x^2-2x}{16-2x^2} \log(3^{-1}) = x \log(4) + \log(3)
x22x162x2(log(3))=xlog(4)+log(3)\frac{x^2-2x}{16-2x^2} (- \log(3)) = x \log(4) + \log(3)
x22x162x2log(3)=xlog(4)+log(3)-\frac{x^2-2x}{16-2x^2} \log(3) = x \log(4) + \log(3)
Divide both sides by log(3)\log(3):
x22x162x2=xlog(4)log(3)+1-\frac{x^2-2x}{16-2x^2} = x \frac{\log(4)}{\log(3)} + 1
x22x162x2=xlog3(4)+1-\frac{x^2-2x}{16-2x^2} = x \log_3(4) + 1
Another approach: let's try to get rid of 4x4^x:
(13)x22x162x2=4x3(\frac{1}{3})^{\frac{x^2-2x}{16-2x^2}} = 4^x \cdot 3
If x=0x=0, then (13)016=403(\frac{1}{3})^{\frac{0}{16}} = 4^0 \cdot 3, so 1=131 = 1 \cdot 3, which means 1=31 = 3, which is false.
If x=1x = -1, then (13)1+2162=(13)314=413=34(\frac{1}{3})^{\frac{1+2}{16-2}} = (\frac{1}{3})^{\frac{3}{14}} = 4^{-1} \cdot 3 = \frac{3}{4}
(13)3140.7534(\frac{1}{3})^{\frac{3}{14}} \approx 0.7534, so 34=0.75\frac{3}{4} = 0.75. Therefore, x=1x=-1 could be an approximate solution.
Let x=2x=-2: (13)4+4168=(13)88=13=423=1163=316(\frac{1}{3})^{\frac{4+4}{16-8}} = (\frac{1}{3})^{\frac{8}{8}} = \frac{1}{3} = 4^{-2} \cdot 3 = \frac{1}{16} \cdot 3 = \frac{3}{16}. This is also false.
Now let's simplify our original equation:
32xx2162x2=4x313^{\frac{2x-x^2}{16-2x^2}} = 4^x \cdot 3^1
32xx2162x21=4x3^{\frac{2x-x^2}{16-2x^2} - 1} = 4^x
32xx216+2x2162x2=4x3^{\frac{2x-x^2-16+2x^2}{16-2x^2}} = 4^x
3x2+2x16162x2=4x3^{\frac{x^2+2x-16}{16-2x^2}} = 4^x
If x=4x = -4, 3168161632=3816=312=33^{\frac{16-8-16}{16-32}} = 3^{\frac{-8}{-16}} = 3^{\frac{1}{2}} = \sqrt{3}. Then 44=12564^{-4} = \frac{1}{256}. So x=4x=-4 is not a solution.
The equation can be rewritten as:
(13)x22x162x2=3(22)x(\frac{1}{3})^{\frac{x^2-2x}{16-2x^2}} = 3 \cdot (2^2)^x
(13)x22x162x2=322x(\frac{1}{3})^{\frac{x^2-2x}{16-2x^2}} = 3 \cdot 2^{2x}
(13)x22x162x2=314x(\frac{1}{3})^{\frac{x^2-2x}{16-2x^2}} = 3^1 \cdot 4^x
32xx2162x2=314x3^{\frac{2x-x^2}{16-2x^2}} = 3^1 \cdot 4^x
Take the natural logarithm of both sides:
ln(32xx2162x2)=ln(314x)\ln(3^{\frac{2x-x^2}{16-2x^2}}) = \ln(3^1 \cdot 4^x)
2xx2162x2ln(3)=ln(3)+xln(4)\frac{2x-x^2}{16-2x^2} \ln(3) = \ln(3) + x \ln(4)
ln(3)(2xx2162x21)=xln(4)\ln(3)(\frac{2x-x^2}{16-2x^2} - 1) = x \ln(4)
2xx2162x21=xln(4)ln(3)\frac{2x-x^2}{16-2x^2} - 1 = x \frac{\ln(4)}{\ln(3)}
2xx2(162x2)162x2=xlog3(4)\frac{2x-x^2 - (16-2x^2)}{16-2x^2} = x \log_3(4)
2xx216+2x2162x2=xlog3(4)\frac{2x-x^2 - 16+2x^2}{16-2x^2} = x \log_3(4)
x2+2x16162x2=xlog3(4)\frac{x^2+2x-16}{16-2x^2} = x \log_3(4)
x2+2x16=xlog3(4)(162x2)x^2+2x-16 = x \log_3(4) (16-2x^2)
x2+2x16=16xlog3(4)2x3log3(4)x^2+2x-16 = 16x \log_3(4) - 2x^3 \log_3(4)
2log3(4)x3+x2+(216log3(4))x16=02 \log_3(4)x^3 + x^2 + (2 - 16\log_3(4))x - 16 = 0
We can observe that if x=2x = 2, the left side of the original equation is (13)44168=(13)0=1(\frac{1}{3})^{\frac{4-4}{16-8}} = (\frac{1}{3})^0 = 1. The right side is 429=163=484^2\sqrt{9} = 16 \cdot 3 = 48.
Consider the case where the exponent x22x162x2=0\frac{x^2-2x}{16-2x^2} = 0. This requires x22x=0x^2-2x = 0, meaning x(x2)=0x(x-2) = 0, so x=0x=0 or x=2x=2. We have already shown x=0x=0 is not a solution. If x=2x=2, we have (13)0=429(\frac{1}{3})^0 = 4^2 \sqrt{9}, or 1=163=481 = 16 \cdot 3 = 48. Thus, x=2x=2 is also not a solution.
Let's test x=2x = -2. (13)4+4168=(13)1=13(\frac{1}{3})^{\frac{4+4}{16-8}} = (\frac{1}{3})^1 = \frac{1}{3}. The right side is 429=1163=3164^{-2} \sqrt{9} = \frac{1}{16} \cdot 3 = \frac{3}{16}.
If x=12x = \frac{1}{2}, then x22x162x2=1411612=34312=34231=362\frac{x^2-2x}{16-2x^2} = \frac{\frac{1}{4}-1}{16-\frac{1}{2}} = \frac{-\frac{3}{4}}{\frac{31}{2}} = -\frac{3}{4} \cdot \frac{2}{31} = -\frac{3}{62}. Then the left side is (13)362=33621.0552(\frac{1}{3})^{-\frac{3}{62}} = 3^{\frac{3}{62}} \approx 1.0552. The right side is 41/23=23=64^{1/2} \cdot 3 = 2 \cdot 3 = 6.
Consider x = -1: (13)1+2162=(13)314(0.3333)0.214=0.7534(\frac{1}{3})^{\frac{1+2}{16-2}} = (\frac{1}{3})^{\frac{3}{14}} \approx (0.3333)^{0.214} = 0.7534. 419=143=34=0.754^{-1} \sqrt{9} = \frac{1}{4} \cdot 3 = \frac{3}{4} = 0.75.

3. Final Answer

x = -1

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