A triangle is a three-sided polygon. It has three interior angles that add up to 180° (a + b + c = 180°). An exterior angle of a triangle is equal to the sum of the two interior angles that are opposite (d = b + c). The perimeter of a triangle is equal to the sum of the lengths of its three sides, the height of a triangle is equal to the length from the base to the opposite vertex (angle) and the area equals one-half triangle base x height: a = ½ base x height.

You need to find the value of b so solve the first equation in terms of x:

6b + x = -4
x = -4 - 6b

then substitute the result (-4 - 6b) into the second equation:

9b - 2(-4 - 6b) = -4
9b + (-2 x -4) + (-2 x -6b) = -4
9b + 8 + 12b = -4
9b + 12b = -4 - 8
21b = -12
b = \( \frac{-12}{21} \)
b = -\(\frac{4}{7}\)

To multiply monomials, multiply the coefficients (the numbers that come before the variables) of each term, add the exponents of like variables, and multiply the different variables together.

(4a)(2ab) + (5a²)(3b)
(4 x 2)(a x a x b) + (5 x 3)(a² x b)
(8)(a¹⁺¹ x b) + (15)(a²b)
8a²b + 15a²b
23a²b

A line on the coordinate grid can be defined by a slope-intercept equation: y = mx + b. For a given value of x, the value of y can be determined given the slope (m) and y-intercept (b) of the line. The slope of a line is change in y over change in x, \({\Delta y \over \Delta x}\), and the y-intercept is the y-coordinate where the line crosses the vertical y-axis.

The formula for area is πr²:

a = πr²
a = π(3²)
a = 9π