Question -
Answer -
(i) (2x + 5)(4x – 3)
= 2x x 4x – 2x x 3 + 5 x 4x – 5 x 3
= 8x² – 6x + 20x -15
= 8x² + 14x -15
(ii) ( y – 8)(3y – 4)
= y x 3y – 4y – 8 x 3y+ 32
= 3y2 – 4y – 24y + 32
= 3y2 – 28y + 32
(iii)(2.5l – 0.5m)(2.5l +0.5m)
= 2.5l x 2.5 l + 2.5l x 0.5m – 0.5m x 2.5l –0.5m x 0.5m
=6.25l2 + 1.25 lm – 1.25 lm – 0.25 m2
=6.25l2– 0.25 m2
iv) (a + 3b) (x + 5)
=ax + 5a + 3bx + 15b
(v) (2pq + 3q2) (3pq – 2q2)
= 2pq x 3pq – 2pq x 2q2 + 3q2 x 3pq – 3q2 x 2q2
= 6p2q2 – 4pq3 + 9pq3 – 6q4
= 6p2q2 + 5pq3 – 6q4
(vi) (3/4 a² + 3b² ) and 4( a² – 2/3 b² )
=(3/4 a² + 3b² ) x 4( a² – 2/3 b² )
=(3/4 a² + 3b² ) x (4a² – 8/3 b² )
=3/4 a² x (4a² – 8/3 b² ) + 3b² x (4a² – 8/3 b² )
=3/4 a² x 4a² -3/4 a² x 8/3 b² + 3b² x 4a² – 3b² x 8/3 b²
=3a4 – 2a² b² + 12 a² b² – 8b4
= 3a4 + 10a² b² – 8b4