№ 1.
1) 1 4/15 + 2 9/10 = 19/15 + 29/10 = (общ.знам.30) = 38/30 + 87/30 = 125/30
2) 7/2 : 125/30 = 105/125 = 21/25 = 0,84
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№2
3х^2 + 4x - 16 = x^2 - 8x + 16
3x^2 - x^2 + 4x + 8x -16 - 16 = 0
2x^2 + 12x - 32 = 0
x^2 + 6x - 16 = 0
D = 36 - 4 (-16) = 36 + 64 = 100; √D = 10
x1 = (- 6 + 10) / 2 = 2
x2 = (-6 - 10)/ 2 = - 8
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№ 3
4х - 28 = 3х
4х - 3х = 28
х = 28
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№ 4
1) 2 3/4 + 1 10/19 = 11/4 + 29/19 = (общ. знам. 76) = 209/76 + 116/76 = 325/76
2) 39/8 : 325/76 = 741/650 = 1 91/650