Factorise x
2
+3x−18.
- A(x+18)(x−1)
- B(x−1)(x+18)
- C(x+6)(x−3)
- D(x−6)(x+3)
Solution & Step-by-step Explanation
To factorise the quadratic expression x
2
+3x−18, we need to find two numbers whose sum is 3 and whose product is −18.
Let the two numbers be a and b.
a+b=3
a×b=−18
The numbers 6 and −3 satisfy both conditions:
6+(−3)=3
6×(−3)=−18
Now, split the middle term:
x
2
+6x−3x−18
Group the terms to take common factors:
x(x+6)−3(x+6)
(x+6)(x−3)
2
+3x−18, we need to find two numbers whose sum is 3 and whose product is −18.
Let the two numbers be a and b.
a+b=3
a×b=−18
The numbers 6 and −3 satisfy both conditions:
6+(−3)=3
6×(−3)=−18
Now, split the middle term:
x
2
+6x−3x−18
Group the terms to take common factors:
x(x+6)−3(x+6)
(x+6)(x−3)