An equation is two expressions separated by an equal sign. The key to solving equations is to repeatedly do the same thing to both sides of the equation until the variable is isolated on one side of the equal sign and the answer on the other.

An isosceles triangle has two sides of equal length. An equilateral triangle has three sides of equal length. In a right triangle, two sides meet at a right angle.

The circumference of a circle is the distance around its perimeter and equals π (approx. 3.14159) x diameter: c = π d. The area of a circle is π x (radius)² : a = π r².

The first step to solve a quadratic expression that's not set to zero is to solve the equation so that it is set to zero:

x² - 15x + 26 = -4x - 2
x² - 15x + 26 + 2 = -4x
x² - 15x + 4x + 28 = 0
x² - 11x + 28 = 0

Next, factor the quadratic equation:

x² - 11x + 28 = 0
(x - 4)(x - 7) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (x - 4) or (x - 7) must equal zero:

If (x - 4) = 0, x must equal 4
If (x - 7) = 0, x must equal 7

So the solution is that x = 4 or 7

A cylinder is a solid figure with straight parallel sides and a circular or oval cross section with a radius (r) and a height (h). The volume of a cylinder is π r²h and the surface area is 2(π r²) + 2π rh.