Question

I have a question for using quadratic equation again. I have 3^2-5x-7=0 Can any one help me?

Answer 1

Do you mean 3x^2?

Answer 2

is nt in the form of quadartic

Answer 3

yes I meant 3x^2-5x-7=0

Answer 4

(3x+7)(x-1)

Answer 5

no sorry

Answer 6

x[1] = 1/6 (5-sqrt(109))
x[2] = 1/6 (5+sqrt(109))

Answer 7

OK doesn't factorise so use formula:

x =( 5 +/- sqrt(25 - 4 times 3 times -7))/3

I get x = (5 +/- sqrt109)/3

Answer 8

?

Answer 9

Do you know the quadratic formula? The solution of ax^2 + bx + c = 0 is

\[x = -b +/- \sqrt{(b^2 - 4ac}) \over 2a\]

Answer 10

yes I know that

Answer 11

@ suzi20 would it not be this x=-5+sqrt109/6, x=-5-sqrt109/6

Answer 12

OK so look at suzi20's correct solution and see if you can get the same answer by substituting for a, b and c in the formula, where a = 3, b = -5 and c = -7

Answer 13

leahp x=-5+sqrt109/6, x=-5-sqrt109/6 is a correct answer

Answer 14

thank you, again

Answer 15

I have one more question does the letter i is not also use for the symbol +- sign together