Simplify : (7x – 8) (3x + 2)

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asked May 16 in Class VIII Maths by muskan15 (-3,360 points)

Simplify :
(i) (7x – 8) (3x + 2)
(ii) (px – q) (px + q)
(iii) (5a + 5b – c) (2b – 3c)
(iv) (4x – 5y) (5x – 4y)
(v) (3y + 4z) (3y – 4z) + (2y + 7z) (y + z)

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1 Answer

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answered May 16 by priya12 (-12,269 points)

(i) (7x – 8) (3x + 2) = 7x(3x + 2) – 8 (3x + 2)

= 21x2 + 14x – 24x – 16 = 21x2 – 10x – 16

(ii) (px –q) (px + q) = px(px + q) – q(px + q)

= p2x2 + pxq – pqx – q2 = p2x2 – q2

(iii) (5a + 5b – c) (2b – 3c)

= 5a (2b – 3c) + 5b(2b – 3c) – c(2b – 3c)

= 10ab – 15ac + 10b2 – 15bc – 2bc + 3c2

= 10ab + 10b2 – 17bc – 15ac + 3c2

(iv) (4x – 5y) (5x – 4y)

= 4x(5x – 4y) – 5y (5x – 4y)

= 20x2 – 16xy – 25xy + 20y2

= 20x2 – 41xy + 20y2

(v) (3y + 4z) (3y – 4z) + (2y + 7z) (y + z)

= 3y (3y – 4z) + 4z(3y – 4z) + 2y(y + z) + 7z(y + z)

= 9y2 – 12yz + 12yz – 16z2 + 2y2 + 2yz + 7yz + 7z2

= (9 + 2)y2 + (-12 + 12 + 2 + 7) yz + (-16  + 7)z2

= 11y2 +9yz – 9z2

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