plz tell me soon ive trying dis for 3 hrs plz reply soon

a = (1,-1)

b = (-2,m)

For two vectors to be collinear, one should be a scalar multiple of the other, that is, a = kb, where k is some scalar.

So, a = kb => i - j = k(-2i + m)

comparing coefficients of i on both sides, 1 = -2k or k = -1/2. Now compare coefficients of j on both sides:

-1 = km but k = -1/2, so m = 2.

For the second question, if two vectors are parallel, then their DR's are proportional. For example,

if ai + bj + ck and di + gj + hk are to be parallel, then a/d = b/g = c/h.

Use this and solve on your own.