Mister Exam
Factor -y^2+y+5 squared
The solution
Factorization
[src]
/ ____\ / ____\ | 1 \/ 21 | | 1 \/ 21 | |x + - - + ------|*|x + - - - ------| \ 2 2 / \ 2 2 /
$$\left(x + \left(- \frac{1}{2} + \frac{\sqrt{21}}{2}\right)\right) \left(x + \left(- \frac{\sqrt{21}}{2} - \frac{1}{2}\right)\right)$$
(x - 1/2 + sqrt(21)/2)*(x - 1/2 - sqrt(21)/2)
The perfect square
Let's highlight the perfect square of the square three-member
$$\left(- y^{2} + y\right) + 5$$
To do this, let's use the formula
$$a y^{2} + b y + c = a \left(m + y\right)^{2} + n$$
where
$$m = \frac{b}{2 a}$$
$$n = \frac{4 a c - b^{2}}{4 a}$$
In this case
$$a = -1$$
$$b = 1$$
$$c = 5$$
Then
$$m = - \frac{1}{2}$$
$$n = \frac{21}{4}$$
So,
$$\frac{21}{4} - \left(y - \frac{1}{2}\right)^{2}$$
$$\left(- y^{2} + y\right) + 5$$
To do this, let's use the formula
$$a y^{2} + b y + c = a \left(m + y\right)^{2} + n$$
where
$$m = \frac{b}{2 a}$$
$$n = \frac{4 a c - b^{2}}{4 a}$$
In this case
$$a = -1$$
$$b = 1$$
$$c = 5$$
Then
$$m = - \frac{1}{2}$$
$$n = \frac{21}{4}$$
So,
$$\frac{21}{4} - \left(y - \frac{1}{2}\right)^{2}$$