# Math Help - Find so that these vectors are mutually perpendicular

1. ## Find so that these vectors are mutually perpendicular

Find c so that these vectors are mutually perpendicular:
a = <c,−2, 3> and b = <c, c,−5>.

how would you go about doing this.

I know how to apply the cross product.

2. Two vectors are perpendicular if their dot product is $\displaystyle 0$.

3. thanks for response and yes i agree if its 0 its mutually perpendicular.

would i have to put a = <c,−2, 3> and b = <c, c,−5> into its determinant form then solve?

4. No, take the dot product and set it equal to $\displaystyle 0$. Then solve the resulting quadratic.

5. ok i see

i got an answer of −3 or it could be 5 i think that's correct

6. Yes that is correct.