Move the variables to one side and the constants to the other
50q - 43 = 52q - 81
50q (-52q) - 43 (+43) = 52q (-52q) - 81 (+43)
50q - 52q = -81 + 43
-2q = -38
isolate the q, divide -2 from both sides
-2q/-2 = -38/-2
q = -38/-2
q = 19
hope this helps

This is found by the volume of a cone formula

Where b is the base and h is the height

Consider the <em>k</em>-th partial sum,

More compactly,

(this is just another case of a similar sum you asked about a while ago [24494877])
The infinite sum is the limit of the partial sum as <em>k</em> goes to infinity. We have

since the non-constant terms in the limit converge to 0.
Alternatively, recall that for |<em>x</em>| < 1, we have

Differentiating both sides gives

also valid for |<em>x</em>| < 1. Take <em>x</em> = 1/<em>π</em> and you get the sum you want to compute.
X=-2
Subtract the 2x from both sides and get 7x-19=-5 and then add 19 to both sides and you get 7x=-14 divide by 7 and x=-2