4題二次公式

何謂二次公式? 公式係 (-b + √(b² - 4ac) ) / 2a ; (-b - √(b² - 4ac) ) / 2a

1. 2x²-3x-2=0 => (--3+√(-3*-3 - 4*2*-2))/(2*2) => (3+√(9+16))/(4) => (3+√25)/4 =>(3+5)/4 => (8/4) => 2,
2x²-3x-2=0 => (--3-√(-3*-3 - 4*2*-2))/(2*2) => (3-√(9+16))/(4) => (3-√25)/4 =>(3-5)/4 =>(-2/4) => -(1/2),

2. 14x²+15-31x=0 => 14x²-31x+15-=0 => (--31+√(31*31 - 4*14*-15))/(2*14) => (31+√(961+840))/(28) => (31+√121)/28 => (31+11)/4 => (42/28) => (3/2)
14x²+15-31x=0 => 14x²-31x+15-=0 => (--31-√(31*31 - 4*14*-15))/(2*14) => (31-√(961+840))/(28) => (31-√121)/28 => (31-11)/4 => (20/28) => (5/7),


3. 3x²-2x-13=0 => (--2+√(-2*-2 - 4*3*-13))/(2*3) => (2+√(4+156))/(6) => (2+√160)/6 => 2+4√10)/6 => (1+2√10)/3

3x²-2x-13=0 => (--2-√(-2*-2 - 4*3*-13))/(2*3) => (2-√(4+156))/(6) => (2-√160)/6 => 2-4√10)/6 => (1-2√10)/3

4. 2x²-6x+3=0 => (--6+√(-6*-6 - 4*2*3))/(2*2) => (6+√(36-24))/(4) => (6+√12)/4 => 6+2√3)/4 => (3+√3)/2

2x²-6x+3=0 => (--6-√(-6*-6 - 4*2*3))/(2*2) => (6-√(36-24))/(4) => (6-√12)/4 => 6-2√3)/4 => (3-√3)/2