1) (х – 4a)(5a + 8x) – (6a – 7х)(3x – 2a);
2) (6c + d)(8с - 9d) + (-10d + 2c)(11c - 4d);
3) (2/3b- 5k)(6k – 0,3b) – (3k + 5/6b) (6b – 1,8k);
4) (1/7x - 1/8y)(7y – 8x)+(y - x)(1/7x – 1/8y).
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