There is only one solution in the given equation -y2 − [-5y − y(-7y − 9)] − [-y (15y + 4)] = 0. In solving this problem, apply first PEMDAS (parenthesis, exponents,multiplication, division, addition, subtraction). Then equation will transform into -y2+5y-7y2-9y+15y2+4y=0. Combine terms with same power and achieve 7y2=0. Divide both sides with 7 and perform square root of zero. Since the root is zero, we have one solution of the given equation which is y=0.
Again, nice problem. These are not super easy. You need to imagine the triangles in the figure and relate sides.
For instance: ADC, its hypotenuse is 15
For ABC, it is 20,
so 20/15 is the ratio between both triangles. Now let's choose the side with 'x'
x is one side of ADC, the corresponding side in ABC is 15 (the second longest sides). You need to rotate the triangles, etc ... That's the tricky part :)
So:
20/15 =15/x ----> x = 15*15/20 = 225/20 = 45/4
Which is C
Not sure whether it's too late to help you though!!!!
Also notice that it's kind of a product rule:
x * 20 = 15 * 15
I am sure the book explains a short way of getting to this equation, like sides opposite, blah blah, but what i told you is the reason. You asked for understanding it! Best luck!
The answer is 7.5 centimeters
X is equal to 30 (vertically opposite angles)
y=180-50
=130 degrees (angles in a straight line equal to 180)
z=180-130-30 (angle sum of a triangle equal to 180)
z=20 degrees
