Respuesta :

riyamaharjan1307

Answer:

18) 6x^2-7x-5

19) 20x^2+17x-63

20) 18x^2-20x+2

21) 5x^2+42x+16

Step-by-step explanation:

Perimeter=length×breadth

18) (3x-5)(2x+1)

=6x^2+3x-10x-5

=6x^2-7x-5

19) (4x+9)(5x-7)

=20x^2-28x+45x-63

=20x^2+17x-63

20) (18x-2)(x-1)

=18x^2-18x-2x+2

=18x^2-20x+2

21) (5x+2)(x+8)

=5x^2+40x+2x+16

=5x^2+42x+16