General simplification
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$$15 b^{2} - b x - x^{2}$$
The perfect square
Let's highlight the perfect square of the square three-member
$$15 b^{2} + \left(- b x - x^{2}\right)$$
Let us write down the identical expression
$$15 b^{2} + \left(- b x - x^{2}\right) = - \frac{61 x^{2}}{60} + \left(15 b^{2} - b x + \frac{x^{2}}{60}\right)$$
or
$$15 b^{2} + \left(- b x - x^{2}\right) = - \frac{61 x^{2}}{60} + \left(\sqrt{15} b - \frac{\sqrt{15} x}{30}\right)^{2}$$
in the view of the product
$$\left(- \sqrt{\frac{61}{60}} x + \left(\sqrt{15} b + - \frac{\sqrt{15}}{30} x\right)\right) \left(\sqrt{\frac{61}{60}} x + \left(\sqrt{15} b + - \frac{\sqrt{15}}{30} x\right)\right)$$
$$\left(- \frac{\sqrt{915}}{30} x + \left(\sqrt{15} b + - \frac{\sqrt{15}}{30} x\right)\right) \left(\frac{\sqrt{915}}{30} x + \left(\sqrt{15} b + - \frac{\sqrt{15}}{30} x\right)\right)$$
$$\left(\sqrt{15} b + x \left(- \frac{\sqrt{15}}{30} + \frac{\sqrt{915}}{30}\right)\right) \left(\sqrt{15} b + x \left(- \frac{\sqrt{915}}{30} - \frac{\sqrt{15}}{30}\right)\right)$$
$$\left(\sqrt{15} b + x \left(- \frac{\sqrt{15}}{30} + \frac{\sqrt{915}}{30}\right)\right) \left(\sqrt{15} b + x \left(- \frac{\sqrt{915}}{30} - \frac{\sqrt{15}}{30}\right)\right)$$
/ / ____\\ / / ____\\
| x*\1 - \/ 61 /| | x*\1 + \/ 61 /|
|b - --------------|*|b - --------------|
\ 30 / \ 30 /
$$\left(b - \frac{x \left(1 - \sqrt{61}\right)}{30}\right) \left(b - \frac{x \left(1 + \sqrt{61}\right)}{30}\right)$$
(b - x*(1 - sqrt(61))/30)*(b - x*(1 + sqrt(61))/30)
Assemble expression
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$$15 b^{2} - b x - x^{2}$$
$$15 b^{2} - b x - x^{2}$$
Combining rational expressions
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$$15 b^{2} + x \left(- b - x\right)$$
$$15 b^{2} - b x - x^{2}$$
$$15 b^{2} - b x - x^{2}$$
$$15 b^{2} - b x - x^{2}$$
Rational denominator
[src]
$$15 b^{2} - b x - x^{2}$$