/ _____\ / _____\
| 7 \/ 157 | | 7 \/ 157 |
|b + - -- + -------|*|b + - -- - -------|
\ 18 18 / \ 18 18 /
$$\left(b + \left(- \frac{7}{18} + \frac{\sqrt{157}}{18}\right)\right) \left(b + \left(- \frac{\sqrt{157}}{18} - \frac{7}{18}\right)\right)$$
(b - 7/18 + sqrt(157)/18)*(b - 7/18 - sqrt(157)/18)
General simplification
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$$9 b^{2} - 7 b - 3$$
The perfect square
Let's highlight the perfect square of the square three-member
$$\left(9 b^{2} - 7 b\right) - 3$$
To do this, let's use the formula
$$a b^{2} + b^{2} + c = a \left(b + m\right)^{2} + n$$
where
$$m = \frac{b}{2 a}$$
$$n = \frac{4 a c - b^{2}}{4 a}$$
In this case
$$a = 9$$
$$b = -7$$
$$c = -3$$
Then
$$m = - \frac{7}{18}$$
$$n = - \frac{157}{36}$$
So,
$$9 \left(b - \frac{7}{18}\right)^{2} - \frac{157}{36}$$
Assemble expression
[src]
$$9 b^{2} - 7 b - 3$$
Rational denominator
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$$9 b^{2} - 7 b - 3$$
Combining rational expressions
[src]
$$b \left(9 b - 7\right) - 3$$