See picture, this one is a little long
Answer:
If two planes would intersect then it would make a line.
Step-by-step explanation:
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Let length be x and breadth be y.
x=y+4
F(x) = 15 <=> 4|x-5| + 3 = 15
<=> 4|x-5| = 12
<=> |x-5| = 3
<=> x-5 = 3 (1) <=> x-5 = -3 (2)
<=> x = 8 (1) <=> x = 2 (2)
x = 8; x = 2