Okay. I have to solve a algebraic expression using a quadratic formula. This is it: X2 - 2X - 6 = 0 I used the quadratic formula on your site here to help me. So... a=1, b=-2, c=-6 X= +3 ± |4 - 4 * 1 - (-6) ------------------------- 2 * 1 = 3 ± |0 ---------- 2 = 3 ± 0 -------- 2 .........and I got 1.5 But when i put it to the equation X2 - 2X - 6 = 0 I get 0.75, it should be 0 right? Does anybody know where i possible went wrong?
Hi Thinker, You appear to be a little off course with this one. Papabravo is correct: --2 = +2. Additionally, what you have in the square root is wrong: If b = -2, then b^2 = +4 And if a = 1 and c = -6, then 4ac = 4*1*-6 = -24 So your expression in the square root is (4 - -24) = +28 If you follow the quadratic equation exactly you should get the answer to be x = +3.64575 or -1.64575 Have another go and post up if you have any problems. Dave
Okay i worked everything out again and this is what i got: (3.64575)2 - (2 * 3.64575) - 6 = 0 13.29150 - 7.2915 - 6 = 0 That is for the 3.64575 answer. I don't know what i was thinking when i put -3 in the equation instead of -2! Thanks Dave and for the help.
Don't forget that x = -1.64575 is also a solution to the equation. This arises due to the fact that there is a +/- in the quadratic formula and provided 4ac =/ 0 then there will be two solutions. Dave