We apply our knowledge in variation.
The solution can be seen in the photo
Answer:
18.1 cm
Step-by-step explanation:
AD segment breakup: 11=4+7
Pythagorean Theorem:
7^2+b^2=16^2
49+b^2=256
x^2=207
b=sqrt(207)
b=3sqrt(23)
Pythagorean Theorem:
11^2+3sqrt(23)^2=c^2
121+207=c^2
328=c^2
18.11=c
So the length of AC is around 18.1 cm
Theorem of cosine:
a²=b²+c²-2bc(cos α) ⇒cos α=-(a²-b²-c²) / 2bc
In this case:
a=15 cm
b=10 cm
c=5 cm
cos α=-(15²-10²-5²) / 2*10*5
cos α=-100 / 100
cos α=-1
A=arc cos -1=180º This is impossible, because:
A+B+C=180º; then B=C=0º This is impossible for make a triangle (B>0 and C>0 if we want to make a triangle).
Therefore: it is not possible can make a triangle with side lengths of 5 cm, 10 cm and 15 cm.
I believe it is 3x+21 but i could be wrong :/ my explaination is -3 • -X would be +3x because it was distributed and -3 • -7 would be +21
