✔ 最佳答案
It usually takes constant practice to be able to solve them without splitting. Nevertheless, I'll do my best and help you.
a. Let's first start with a quadratic with a =1
example: x^2 + x - 6, where a=1, b=1, c= -6
First create two brackets : ( ) ( )
then place x in the first positions of both brackets: (x )(x )
then find the two numbers that multiplies to get -6. i.e. 2 and 3
since b=1 (ie,its positive), the bigger one should be positive
therefore, we get
(x + 3)(x - 2)
try with x^2 + 5x - 6
if you get this right, then you are ready for the next challenge, a quadratic with a > 1
For example: 3x^2+17x+10, a=3, b=17, c=10
We still create our two brackets, but place 3x in the first and x in the second:
(3x )(x )
Why? Because the first term is 3x^2
Then find the two numbers that multiply to get 30 (remember to multiply a and c) and add up to get 17. That will be 15 and 2
Now, instead of fixing in the 15, remember that, when you expand, you'll have to come back to the same question, and since we already have 3x in one bracket, then we'll need just a 5
Therefore, we get
(3x + 2) (x + 5)
As I said, this comes by continuous practice. Try working as many examples as you can, and I know you'll get there. All the best!