Solve the equation using the method of factorisation- x2 - 4x - 45 = 0

x² + 4x -9= (x + a)^2 + b
Find the value of a and the value of b.

X = 9,X= -5, a =  2, b = -13

Step-by-step explanation:

For (1),

Using Cross-factorization,

it can be reduced to (X - 9)(X + 5) = 0

Equate each factor to 0:

we have X = 9 and X = -5

For (2),

It is the case of completing the Square,

add 4 so we get the completed square ( we want the form X^2 + 2a + a^2)

(X^2 + 4X + 4) - 9

can be simplified to (X+2)^2 -9

However since we added 4 it means we have to subtract 4

So it becomes (X+2)^2 -9 -4

= (X+2)^2 -13