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Given: Picture 20×30 cm, border width = x, border area = picture area
Area_picture = 20×30 = 600 cm²
Area_total = (30 + 2x)(20 + 2x)
Area_border = Area_total - 600 = 600 (30 + 2x)(20 + 2x) = 1200
Expand: 4x² + 100x + 600 = 1200 4x² + 100x - 600 = 0 x² + 25x - 150 = 0
Solve: x = [-25 ± (25² - 4(1)(-150))]/2 x = 5 or -30
Discard negative x = 5 cm
Answer: Border width = 5 cm
Added 59 days ago|11/21/2025 9:42:53 AM
This answer has been confirmed as correct and helpful.
