   SEARCH HOME Math Central Quandaries & Queries  Subject: find the product of each Name: jennifer Who are you: Student I am having a hard time with math please help me. Find the product of each (8x)(-4) (3x)(5y)(7z) (8x^3y)-5X^2) (6a)(3a)(-b^2) Hi Jennifer,

There is an understood multiplication symbol between the 8 and the x in 8x. Likewise there is an understood multiplication symbol between (8x) and (-4). Thus you can think of (8x)(-4) as (8 times x) times (-4) or with symbols

(8 x) (-4)

Since multiplication is commutative (that is you can perform a string of multiplications in any order you want) you can write this as

(8) (-4) x = -32 x

Again using the convention of the understood multiplication

-32 x = -32x

Thus

(8x)(-4) = -32x

Now let me try the 4th problem, (6a)(3a)(-b2). Making the understood multiplication explicit this is

(6 a) (3 a) (-b2)

and using the commutative property of multiplication

(6 a) (3 a) (-b2) = 6 3 a a (-b2) = 18 a2 b2 = 18a2b2

Penny     Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.