To combine like terms, add or subtract the coefficients (the numbers that come before the variables) of terms that have the same variable raised to the same exponent.

2a - 6a = -4a

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

z² - 5z + 4 = 0
(z - 1)(z - 4) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (z - 1) or (z - 4) must equal zero:

If (z - 1) = 0, z must equal 1
If (z - 4) = 0, z must equal 4

So the solution is that z = 1 or 4

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.

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

sa = 2πr² + 2πrh
sa = 2π(7²) + 2π(7 x 2)
sa = 2π(49) + 2π(14)
sa = (2 x 49)π + (2 x 14)π
sa = 98π + 28π
sa = 126π

A parallelogram is a quadrilateral with two sets of parallel sides. Opposite sides (a = c, b = d) and angles (red = red, blue = blue) are equal. The area of a parallelogram is base x height and the perimeter is the sum of the lengths of all sides (a + b + c + d).