Question

If a * b = 2a – 3b + ab, then 5 * 7 + 7 * 5 is equal to:

Answer 1

Answer:

5*7+5*7

=35+35

=70

Explanation:

This is the associative property of numbers which means that if we change the positions of numbers in multiplication and addition the answer does not really change this law is not applicable for subtraction and division

Answer 2

Answer:

5 * 7 +  5 * 7 = 58

Explanation:

Given that

a * b = 2a – 3b + ab                        -------------1

We have to find  5 * 7 + 7 * 5

First lets find  5 * 7:

If we compare  5 * 7 from equation 1 then we will get

a = 5 ,b=7

So

5 * 7 = 2 *5 - 3*7 + 5 *7                     ( a * b = 2a – 3b + ab     )

5 * 7 = 10- 21 + 35

5 * 7 = 45 - 21

5 * 7= 24        -----------------2

Now lets find 7 * 5:

Here

a =7   ,b=5        

7 * 5 = 2*7 - 3*5 +7*5

7 * 5 = 14 - 15 + 35

7 * 5 =34                ----------------3

Now by adding equation   2 and 3

5 * 7 +  5 * 7 = 24 + 34

5 * 7 +  5 * 7 = 58