If a=2i-3j-k and b=i+4j+2k what us ab

2i²+5ij+3ik-12j²-10jk-2k²

Step-by-step explanation:

a=2i-3j-k

b=i+4j+2k

ab = (2i-3j-k) (i+4j+2k)

Multiply both bracket by expanding the bracket

2i(i+4j+2k)-3j(i+4j+2k)-k(i+4j+2k)

Multiply

2i²+8ij+4ik-3ij-12j²-6jk-ik-4jk-2k²

Collect like terms

2i²+8ij-3ij+4ik-ik-12j²-6jk-4jk-2k²

2i²+5ij+3ik-12j²-10jk-2k²

256π units²   (answer b)

step-by-step explanation:

the formula for the surface area of a sphere of radius r

is             a = 4πr²

and so, if r = 8 units, then the surface area is:

a = 4π(8 units)² = 256π units²   (answer b)

10 * 563.67 = 5636.7