Question

GIVE ME EXPANSION OF THIS = (a+7) (a-15)

Answer 1

(a+7)(a-15) = a(a)+a(-15)+7(a)+7(-15)

= a^2-15a+7a-105

Answer 2

       Method 1 for the solution :

⇒ ( a + 7 )( a - 15 )

⇒ a( a - 15 ) + 7( a - 15 )

⇒ a^2 - 15a + 7a -  105

⇒ a^2 - 8a - 105

            Method 2 for the solution :

( a + 7 )( a - 15 )

We know, ( a + b )( a - c ) = a^2 + ( b + c )a + bc

⇒ ( a + 7 )( a - 15 )

⇒ a^2 + { 7 + ( - 15 ) }a + ( - 15 x 7 )

⇒ a^2 + ( 7 - 15 )a - 105

⇒ a^2 - 8a - 105

Therefore expansion of ( a + 7 )( a - 15 ) is a^2 - 8a - 105.