Question

find the values of m so that the equation x2+ mx + 4=0 has equal roots

Answer 1

if the equation must have equal roots then b²-4ac=0
b=m   a=1   c=4
m²-4(4)=0
m²-16=0
m²=16
m=√16
m= + or - 4

Answer 2

For equal roots,,
D = 0
→ b²-4ac = 0
→ m²-4*1*4 = 0
→ m²-16 = 0
→ (m)²-(4)² = 0
→ (m+4)(m-4) = 0
→ m+4 = 0 or m-4 = 0
so, m = -4 or 4