I need help. ​

4

Step-by-step explanation:

Break down the shape into a rectangle and a triangle

To find the base of the triangle subtract

(3x-1)-(x+1)= 2x-2

which means the area of the triangle is

.5(2x-2)(x-1)= x²-2x+1

Let's then find the area of the rectangle

(x+1)(x-1)= x²-1

Take the sum and set this equal to 40

(x²-2x+1)+(x²-1)=40

simplify...

2x²-2x-40=0

x²-x-20=0

(x-5)(x+4)=0

Reject the negative answer and get x=5

Then it's just a matter of plugging in x=5 for the height (x-1)

5-1=4 which is the final answer

4 cm.

Step-by-step explanation:

Area formulas:

A(Rectangle) = bh

A(Triangle) = 1/2bh

A(Trapezium) = A(Rectangle) + A(Triangle)

Use the information given and substitute the values to solve for the missing height:

A(Rectangle) + A(Triangle) = A(Trapezium)

bh + 1/2bh = 40

(x + 1)(x - 1) + 1/2(2x - 2)(x - 1) = 40

x² - 1 + x² - 2x + 1 = 40

2x² - 2x = 40

2x² - 2x - 40 = 0

Use Quadratic Formula to solve for x:

a = 2, b = -2, c = -40

x = (-b ± √(b² - 4ac))/2a

x = (-(-2) ± √((-2)² - 4(2)(-40)))/2(2)

x = (2 ± 18)/4

x = 5 and x = -4

Since we cannot have a negative height, we use x = 5:

h = (5) - 1 = 4

Therefore, the height of the trapezium is 4 cm.

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