Question #7a5e5

1 Answer
Dec 8, 2017

#(1): vecA*(3vecB-vecC)=37.#

#(2): vecA*(vecBxxvecC)=180.#

#(3): vecBxx(vecAxxvecC)=-87i-21j-66k.#

Explanation:

We have, #vecA=2i+6j+k=(2,6,1).#

#vecB=(-3,3,3), and, vecC=(5,-1,4).#

#:. 3vecB-vecC=3(-3,3,3)-(5,-1,4),#

#=(-9,9,9)-(5,-1,4),#

#=(-9-5,9-(-1),9-4),#

# rArr 3vecB-vecC=(-14,10,5).#

#:. vecA*(3vecB-vecC)=(2,6,1)*(-14,10,5),#

#=2(-14)+6*10+1.5,#

#=-28+60+5.#

# rArr vecA*(3vecB-vecC)=37.................................................(1).#

(2) : #vecA*(vecBxxvecC).#

#vecBxxvecC=|(i,j,k),(-3,3,3),(5,-1,4)|,#

#=(12-(-3))i-(-12-15)j+(3-15)k,#

#=15i+27j-12k,#

#:. vecBxxvecC=(15,27,-12).#

#:. vecA*(vecBxxvecC)=(2,6,1)*(15,27,-12),#

#=2*15+6*27+1(-12),#

#=30+162-12.#

#rArr vecA*(vecBxxvecC)=180.................................................(2).#

OR,

# vecA*(vecBxxvecC)=|(2,6,1),(-3,3,3),(5,-1,4)|,#

#=2|(3,3),(-1,4)|-6|(-3,3),(5,4)|+1|(-3,3),(5,-1)|,#

#=2(12-(-3))-6(-12-15)+1(3-15),#

#=2.15-6(-27)+1(-12),#

#=30+162-12.#

# rArr vecA*(vecBxxvecC)=180,# as before!..........................#(2).#

(3) : #vecBxx(vecAxxvecC)#

#vecAxxvecC=|(i,j,k),(2,6,1),(5,-1,4)|=(25,-3,-32),#

#:. vecBxx(vecAxxvecC)=|(i,j,k),(-3,3,3),(25,-3,-32)|,#

#=(-96+9)i-(96-75)j+(9-75)k.#

# rArr vecBxx(vecAxxvecC)=-87i-21j-66k..............(3).#