A right angle measures 90 degrees and is the intersection of two perpendicular lines. In diagrams, a right angle is indicated by a small box completing a square with the perpendicular lines.

The area of a triangle is equal to ½ base x height:

a = ½bh
a = ½ x 6 x 9 = \( \frac{54}{2} \) = 27

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.

For parallel lines with a transversal, the following relationships apply:

• angles in the same position on different parallel lines equal each other (a° = w°, b° = x°, c° = z°, d° = y°)
• alternate interior angles are equal (a° = z°, b° = y°, c° = w°, d° = x°)
• all acute angles (a° = c° = w° = z°) and all obtuse angles (b° = d° = x° = y°) equal each other
• same-side interior angles are supplementary and add up to 180° (e.g. a° + d° = 180°, d° + c° = 180°)

Applying these relationships starting with b° = 147, the value of d° is 147.

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:

a² - 10 = -4a - 5
a² - 10 + 5 = -4a
a² + + 4a - 5 = 0
a² + 4a - 5 = 0

Next, factor the quadratic equation:

a² + 4a - 5 = 0
(a - 1)(a + 5) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (a - 1) or (a + 5) must equal zero:

If (a - 1) = 0, a must equal 1
If (a + 5) = 0, a must equal -5

So the solution is that a = 1 or -5