Mister Exam
Factor y^4+y^2-15 squared
The solution
The perfect square
Let's highlight the perfect square of the square three-member
$$\left(y^{4} + y^{2}\right) - 15$$
To do this, let's use the formula
$$a y^{4} + b y^{2} + c = a \left(m + y^{2}\right)^{2} + n$$
where
$$m = \frac{b}{2 a}$$
$$n = \frac{4 a c - b^{2}}{4 a}$$
In this case
$$a = 1$$
$$b = 1$$
$$c = -15$$
Then
$$m = \frac{1}{2}$$
$$n = - \frac{61}{4}$$
So,
$$\left(y^{2} + \frac{1}{2}\right)^{2} - \frac{61}{4}$$
$$\left(y^{4} + y^{2}\right) - 15$$
To do this, let's use the formula
$$a y^{4} + b y^{2} + c = a \left(m + y^{2}\right)^{2} + n$$
where
$$m = \frac{b}{2 a}$$
$$n = \frac{4 a c - b^{2}}{4 a}$$
In this case
$$a = 1$$
$$b = 1$$
$$c = -15$$
Then
$$m = \frac{1}{2}$$
$$n = - \frac{61}{4}$$
So,
$$\left(y^{2} + \frac{1}{2}\right)^{2} - \frac{61}{4}$$
Factorization
[src]
/ ____________\ / ____________\ / ______________\ / ______________\ | / ____ | | / ____ | | / ____ | | / ____ | | / 1 \/ 61 | | / 1 \/ 61 | | / 1 \/ 61 | | / 1 \/ 61 | |x + I* / - + ------ |*|x - I* / - + ------ |*|x + / - - + ------ |*|x - / - - + ------ | \ \/ 2 2 / \ \/ 2 2 / \ \/ 2 2 / \ \/ 2 2 /
$$\left(x - i \sqrt{\frac{1}{2} + \frac{\sqrt{61}}{2}}\right) \left(x + i \sqrt{\frac{1}{2} + \frac{\sqrt{61}}{2}}\right) \left(x + \sqrt{- \frac{1}{2} + \frac{\sqrt{61}}{2}}\right) \left(x - \sqrt{- \frac{1}{2} + \frac{\sqrt{61}}{2}}\right)$$
(((x + i*sqrt(1/2 + sqrt(61)/2))*(x - i*sqrt(1/2 + sqrt(61)/2)))*(x + sqrt(-1/2 + sqrt(61)/2)))*(x - sqrt(-1/2 + sqrt(61)/2))
Combining rational expressions
[src]
2 / 2\ -15 + y *\1 + y /
$$y^{2} \left(y^{2} + 1\right) - 15$$
-15 + y^2*(1 + y^2)