State whether each expression is meaningful. if not, explain why. if so, state whether it is a vector or a scalar. (a) a · (b × c. the expression is meaningful. it is a vector. the expression is meaningful. it is a scalar. the expression is meaningless. the cross product is defined only for two vectors.

we are given

a · (b × c)

we know that

cross product of two vectors are vector

and dot product of two vectors are scalar

(b × c) is cross product of vectors b and c

so,(b × c) = vector

a ·( vector) is dot product of two vectors

so, a ·( vector) = scalar

so, this expression is meaningful

and

a · (b × c) = scalarAnswer

f(x) has value 150 at x= 0

and 0 at x= 3

so d(f(x))/dt = slope = -150/3 = -50