By using standard formulae, solve the following: 1.(x-7)(x+9) 2. (X + 2 y + 3)(x + 2 y + 7) 3. (2x + y + 5 )(2x + y - 9) 4.(x - 2y - 5) (x - 2y + 3) 5.(3x-4 y - 2) (3x -4 y - 6) 6.if a^2 + 4 a + x ={a + 2 }^2 find the value of x. 7.( 27)^3 + (-17)^3+(-10)^3 8. (-28)^3+(15)^3+(13)^3 Please tell the answers experts.. I ask many questions but no one tells the answer.Please clear all my doubts.