[multiplying monomials][section 32]

(1.)   x4 * x5                       here is the problem

=      x9                      add exponents

result:    x9

(2.)  (-4x2y)(-5xy)             here is the problem

=     20x3y2                multiply, add exponents

result:  20x3y2

(3.)  (8mn2)(-3m2y4)          here is the problem

=    -24m3n6            multiply, add exponents

result:  -24m3n6

(4.)  (4c2d)(5cd)(cd2)       here is the problem

=     20c4d4        multiply add exponents

result:  20c4d4

(5.)  (2x)(3x4)(-6x3)          here is the problem

=      -36x8       multiply add exponents

result:  -36x8

(6.)  (-2x4)(-3x2)          here is the problem

=        6x6              multiply add exponents

result:  6x6

(7.)   (-x5)(5xy2)(9x3y2)      here is the problem

=     -45x9y4              multiply add exponents
result:  -45x9y4

(8.)  (-3a2b)(ab)(-2ab)0             here is the problem

=     (-3a2b)(ab)(1)         anything to the 0 power is 1

=     -3a3b2                     multiply add exponents

result:  -3a3b2

(9.)  103 * 102 * 104               here is the problem

=        109                      add exponents

result:  109

(10.)   xa * xb                  here is the problem

=      x(a+b)                   add exponents

result:  x(a+b)