Answer:
34
first of all use formula:
n(AUB)=n(A)+n(B)-n(AnB)
Answer: 4 dollars for each notebook
Step-by-step explanation:
21-9= 12
12/3=4
each notebooks costs 4 dollars
To find W⊥, you can use the Gram-Schmidt process using the usual inner-product and the given 5 independent set of vectors.
<span>Define projection of v on u as </span>
<span>p(u,v)=u*(u.v)/(u.u) </span>
<span>we need to proceed and determine u1...u5 as: </span>
<span>u1=w1 </span>
<span>u2=w2-p(u1,w2) </span>
<span>u3=w3-p(u1,w3)-p(u2,w3) </span>
<span>u4=w4-p(u1,w4)-p(u2,w4)-p(u3,w4) </span>
<span>u5=w5-p(u4,w5)-p(u2,w5)-p(u3,w5)-p(u4,w5) </span>
<span>so that u1...u5 will be the new basis of an orthogonal set of inner space. </span>
<span>However, the given set of vectors is not independent, since </span>
<span>w1+w2=w3, </span>
<span>therefore an orthogonal basis cannot be found. </span>

now, the one below that, which is equivalent to that? well, just look above it
If the negative square root is found to be one of your solutions, then that is indicative of a pair of imaginary roots (the imaginary i). According to the conjugate rule, if you have one solution that is imaginary, you will have another but with the opposite sign. For example, if a solution to a quadratic is found to be 2 - i, then its conjugate, 2 + i is also a solution. They will ALWAYS go in pairs. Same thing with radical solutions. If one solution is found to be 
then
will also be a solution.