I want answer of question no.19

I want answer of question no.19 Let 3x — 2y = a Given expression = 12(3x — 2y)2 — (3x — 2Y) -1 x2y2 and so on. -7b (7a-7b) 6-7-3-3 16. 19. 20. = 12a2 —a—I and soon. 14. 4(2x - 3y)2 - 8x + 12y-3 15. 3-5x+5y- 9x2 + 3x — Sy — 64y2 17. 1 18. — (a + — — (2a — 16 4 2(ab + cd) — a2 — b2 + c2 + d2 diSi Find the value of : (i) (987)2 - (13)2 (67) 2 - (3-3)2 (iii) (ii) (67-8)2 - (320 (iv) 18-5+65 76