Answer:
In a product like:
a*b = 0
says that one of the two terms (or both) must be zero.
Here we have our equation:
x^2 + 12 = 7x
x^2 + 12 - 7x = 0
Let's try to find an equation like:
(x - a)*(x - b) such that:
(x - a)*(x - b) = x^2 + 12 - 7x
we get:
x^2 - a*x - b*x -a*-b = x^2 - 7x + 12
subtracting x^2 in both sides we get:
-(a + b)*x + a*b = -7x + 12
from this, we must have:
-(a + b) = -7
a*b = 12
from the first one, we can see that both a and b must be positive.
Then we only care for the option with positive values, which is x =3 or x = 4
replacing these in both equations, we get:
-(3 + 4) = -7
3*4 = 12
Both of these equations are true, then we can write our quadratic equation as:
(x - 3)*(x - 4) = x^2 + 12 - 7x
The correct option is the last one.
