Key idea: Method 1: Factorisation
Rewrite ax2+bx+c=0 as a product (px+q)(rx+s)=0, then use the **zero-product property**: a product is zero iff one of its factors is zero.
**Steps for x2+bx+c=0∗∗(a=1):
1. Find two numbers that MULTIPLY to c and ADD to b.
2. Use them as the constants in (x+p)(x+q).
**Example**: x2−7x+12=0 → product 12, sum −7 → numbers −3 and −4 → (x−3)(x−4)=0 → x=3 or 4.
**For ax2+bx+c with a ≠ 1**: split the middle term — find two numbers multiplying to a×c and summing to b. Then group.
Example: 2x2+7x+3=0.a×c=6, sum = 7 → 6 and 1. Split: 2x2+6x+x+3=2x(x+3)+1(x+3)=(2x+1)(x+3)=0 → x=−1/2 or −3.