- theo hệ thức Vi - et ta có
x1 + x2 =6
x1 × x2 = m
1) x1 - x2 = 10
=> (x1 - x2)^2 = 10^2
=> x1^2 + x2^2 - 2x1 × x2 = 100
=> (x1 + x2)^2 - 4x1 × x2 = 100
=>6^2 - 4m = 100
=> m = - 16
2)x1^2 - x2^2 =42
=> (x1 + x2)^2 - 2x1 × x2 = 42
=> 6^2 - 2m = 42
=> m =-3
3)x1^2 - x2^2 = 26
=> (x1 + x2)^2 - 2x1 × x2 = 26
=> 6^2 - 2m = 26
=> m = 5
4)x1 + x2 = 6
=> x1 = 6 - x2
x1 = 2x2
=> 6 - x2 = 2x2
=> x2 = 2
=> x1 = 6 - 2 = 4
=> m = 2 × 4 = 8
5) x1 + x2 = 6
=> x2 = 6 - x1
3x1 + x2 = 8
=> 3x1 + 6 - x1 = 8
=> x1 = 1
=> x2 = 6 - 1 = 5
=> m = 1× 5 = 5
