Okay so the area of a rectangle x by y with a border of width b will be:
A=(x+2b)(y+2b)
A=xy+2bx+2by+4b^2 we are told that A=320, x=11, and y=15 so now we have:
320=165+22x+30x+4x^2, now I am using x as the border width...
4x^2+55x+165=320 is the equation that they listed..
...
4x^2+55x-155=0 using the quadratic formula for efficiency...
x=(-55±√5505)/8 since x>0
x≈2.399 which for some unknown (incorrect) reason they rounded to
x=2.5
So in short, your answer is a)
for my guess I would say about 45 I might be wrong but im pretty sure
Answer:
x=6, x=-5
Step-by-step explanation:
Factoring this quadratic gets you (x-6)(x+5)=0, for this to be possible, either x-6 or x+5 has to be zero, so therefor x is 6, or x is -5
R=17/3 alternative form would be r= 5 2/3, r=5.6 those would all be the answers depending on what form you need