Question

Please help! foil the problems 1. (3xy - 1) (4xy + 2) 2. (2x - 3y)(4x - y) 3. (ab - 9)(ab + 8) 4. (m 3 n + 8)(m 3 n - 5) 5. (3 - c 2 d)(4 - 4c 2 d) 6. (1 - 7x)(1 + 9x) 7. (3m 3 - y)(3m 3 - y) 8. (a + b)(a 2 - ab + b 2) 9. (a - b)(a 2 + ab + b 2) 10. (a + b - c)(a + b + c) 11. (x 2 + 2x - 1)(x 2 + 2x + 5) 12. [4 - (3c - 1)][6 - ( 3c - 1)] 13. (x + y + 3)(x + y - 4)

Answer 1

I am going to do the first 2 problems and show my work that way you know how to do it yourself.

So first of all, the foil method:

(a+b) (c+d) = ac+ad+bc+bd

1. (3xy-1) (4xy+2) = (3xy*4xy) + (3xy*2) + (-1*4xy) + (-1*2)

    (3xy-1) (4xy+2) = (12x^2y^2) + (6xy) + (-4xy) + (-2)
    
    (3xy-1) (4xy+2) = (12x^2y^2) + (6xy-4xy) - 2

    (3xy-1) (4xy+2) = 12x^2y^2 + 2xy - 2

2. (2x-3y) (4x-y) = (2x*4x) + (2x*-y) + (-3y*4x) + (-3y*-y)

    (2x-3y) (4x-y) = (8x^2) + (-2xy) + (-12xy) + (3y^2)

    (2x-3y) (4x-y) = 8x^2 + (-2xy-12xy) + 3y^2

    (2x-3y) (4x-y) = 8x^2 - 14xy + 3y^2

I hope this helps!