The first step to solve a quadratic equation that's set to zero is to factor the quadratic equation:

b² + 7b - 18 = 0
(b - 2)(b + 9) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (b - 2) or (b + 9) must equal zero:

If (b - 2) = 0, b must equal 2
If (b + 9) = 0, b must equal -9

So the solution is that b = 2 or -9

The surface area of a cylinder is 2πr² + 2πrh:

sa = 2πr² + 2πrh
sa = 2π(1²) + 2π(1 x 7)
sa = 2π(1) + 2π(7)
sa = (2 x 1)π + (2 x 7)π
sa = 2π + 14π
sa = 16π

The formula for area is πr²:

a = πr²
a = π(4²)
a = 16π

To solve this equation, isolate the variable for which you are solving (a) on one side of the equation and put everything else on the other side.

-9a - 4y = -3a + 5y + 2
-9a = -3a + 5y + 2 + 4y
-9a + 3a = 5y + 2 + 4y
-6a = 9y + 2
a = \( \frac{9y + 2}{-6} \)
a = \( \frac{9y}{-6} \) + \( \frac{2}{-6} \)
a = -1\(\frac{1}{2}\)y - \(\frac{1}{3}\)

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.