Q15 of 59 Page 162

If a = 3x – 5y, b = 6x + 3y and c = 2y – 4x, find

(i) a + b – c;


(ii) 2a–3b + 4c.

(i) a + b – c = 3x – 5y + 6x + 3y-2y + 4x


⇒ a + b – c = 13x - 4y


(ii) 2a–3b + 4c = 2(3x – 5y) + 3(6x + 3y)-4(2y – 4x)


⇒ 2a–3b + 4c = 6x-10y + 18x + 9y-8y + 16x


⇒ 2a–3b + 4c = 40x-9y


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