Question

Multiply (78 + 11b) by (13a +9b) and find the for a=1 and b=-1​

Answer 1

In context to the question it is asked to find the value by multiplying to equation the following are the data given

a=1

b=-1

equation 1=(78+11b)

                by putting value we get

                =$(78 +(11\times -1)$

$78+(-11)\\=78-11\\=67$

equation 2 = (13a+9b)

by putting the value

              $(13\times1+9\times-1)\\=(13+(-9)\\\\=(13-9)\\=4$

now in question it is asked to multiply  hence

equation 1 x equation 2

$67\times4\\=268$

so final conclusion is 268 for this equation