Question

1. One of the solutions to the quadratic equation x2 - 13x + 30 is 3 whats another?
2. and one of the solutions to the quadratic equation 2x2 - 9x – 5 is -1/2 whats also another ?

Answer 1

Are you just checking your answer, or do you want an explanation?

Answer 2

well im just checking and i need to write down two for each so im unsure whats the other

Answer 3

factorise the quadratic

factors of 30 that add to -13....... -10, -3

(x -3)(x-10) = 0

you can finish

Answer 4

first one is 10, second one is 5.

Answer 5

(2) 2 x -5 = -10 find the factors of -10 that add to -9.... -10 and 1

(2x -10)(2x+1)/2 = 2(x - 5)(2x + 1)/2

gives

(x - 5)(2x + 1) = 0

you can finish this one

Answer 6

The product of the two roots of
\[ a x^2 + b x + c=0\]
is \[\frac c a\]
for the first quadratic the product of the two roots is
\[\frac c a = \frac {30}1 = 30
\]
If one of the roots is 3, what is the other one.

Answer 7

That's interesting, I didn't know there was a formula for the product of the roots.

Answer 8

For the second one
\[ \frac c a = - \frac 5 2
\]
The first root is \[ -\frac 1 2
\]
The second must be 5.

Answer 9

sum of the roots
\[\alpha + \beta = -b/a\]

Answer 10

@campbell_st, you can do it this way two.
Problems like this can be found on
http://www.saab.org/mathdrills/act.html