Question

find the scalar and vector product of a=3i+4j and b=-3i+7j

Answer 1

Scalar product- (3i+4j).(-3i+7j)=19.
as

3i×(-3i)=-9 as (i×i=1)
4j×7j=28 as (j×j=1)

vector product-
(3i+4j)×(-3i+7j)=21i+12j
as
multiplying 'i' term of 1st vector with 'j' term of 2nd vector gives us 21
and
-ve of product of 'j' term of first vector and 'i' term of 2nd vector (i.e. -3×4) gives us 12
hence the answer
21i+12j

Answer 2

sorry in vector product
it's + k[(3×7)-(4×-3)] in 11th line without including the blank lines.