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Let v_1, v_2, v_3 be the vectors in R^3 defined by v_1 = [-28 29 -2] v_2 = [12 -

ID: 3036370 • Letter: L

Question

Let v_1, v_2, v_3 be the vectors in R^3 defined by v_1 = [-28 29 -2] v_2 = [12 -11 13] v_3 [16 -18 -11] (a) Is {v_1, v_2, v_3} linearly independent? Write all zeros if it is or if it is linearly dependent write zero as a non-trivial (not all zero coefficients) linear combination of v_1, v_2, and v_3 (b) Is {v_1, v_2} linearly independent? Write all zeros if it is or if it is linearly dependent write zero as a non-trivial (not all zero coefficients) linear combination of v_1 and v_2 (c) Type the dimension of span {v_1, v_2, v_3}:

Explanation / Answer

Let A =

-28

12

16

29

-11

-18

-2

13

-11

We will reduce A to its RREF as under:

Multiply the 1st row by -1/28

Add -29 times the 1st row to the 2nd row

Add 2 times the 1st row to the 3rd row

Multiply the 2nd row by 7/10

Add -85/7 times the 2nd row to the 3rd row

Add 3/7 times the 2nd row to the 1st row

Then the RREF of A is

1

0

-1

0

1

-1

0

0

0

(a) Apparently, the set {v1,v2,v3} is linearly dependent and v3 = -v1-v2 or, v1+v2+v3 = 0

(b) The set {v1,v2} is linearly independent.

(c) The dimension of the span {v1,v2,v3} is 2 as the set {v1,v2,v3} is linearly dependent and the set {v1,v2} is linearly independent.

-28

12

16

29

-11

-18

-2

13

-11