2/3^x²+5x>1
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20 января 2025 13:48
To solve the inequality ( \frac{2}{3^{x^2 + 5x}} > 1 ), we will first manipulate the inequality to get it in a more manageable form.
Start by rewriting the inequality: [ \frac{2}{3^{x^2 + 5x}} > 1 ]
To eliminate the fraction, multiply both sides by ( 3^{x^2 + 5x} ) (noting that since (3^{x^2 + 5x}) is positive for all real (x), the direction of the inequality does not change): [ 2 > 3^{x^2 + 5x} ]
Now, we can express this as: [ 3^{x^2 + 5x} < 2 ]
To solve for ( x^2 + 5x ), take the logarithm (base 3) of both sides: [ x^2 + 5x < \log_3(2) ]
Let's denote ( c = \log_3(2) ), making the inequality: [ x^2 + 5x - c < 0 ]
Now, we will solve the quadratic inequality ( x^2 + 5x - c < 0 ). To do this, we need to find the roots of the quadratic equation: [ x^2 + 5x - c = 0 ]
Using the quadratic formula ( x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} ): [ x = \frac{-5 \pm \sqrt{25 + 4c}}{2} ]
The roots are: [ x_1 = \frac{-5 - \sqrt{25 + 4c}}{2}, \quad x_2 = \frac{-5 + \sqrt{25 + 4c}}{2} ]
The quadratic ( x^2 + 5x - c ) will be less than 0 between the two roots ( x_1 ) and ( x_2 ). Thus, the solution to the inequality ( x^2 + 5x - c < 0 ) is: [ x_1 < x < x_2 ]
Finally, substituting back for ( c = \log_3(2) ): [ \frac{-5 - \sqrt{25 + 4\log_3(2)}}{2} < x < \frac{-5 + \sqrt{25 + 4\log_3(2)}}{2} ]
This gives you the solution set for the original inequality. You can now evaluate the numerical values of ( x_1 ) and ( x_2 ) using a calculator if needed.
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