6x + 15 is the formula for the triangle's perimeter. Let x represent the triangle's bottom. The length of one side of a triangle equals 12 times the length of the triangle's bottom, so: 4x + 12 is the side length. The last side of the triangle is three times longer than the bottom, resulting in: x + 3 is the length of a side. Triangle perimeter = x + (4x + 12) + (x + 3) 6x + 15 = Perimeter 6x + 15 is the formula for the triangle's perimeter.
We know that applying the law of cosines a² = b²+ c²<span> – 2*b*c*cos(A) </span> in this problem a=? b=20 c=9 A=90° so a² = b²+ c² – 2*b*c*cos(A) but cos (A)=0 a² = b²+ c²-----> 20²+9²----> a²=400+81----> a²=481-----> a=√481 a=21.93-----> a=22
