If x+y=5,x-y=4,find the value of x²-y²

20

Step-by-step explanation:

→ First find the value of x and y

x + y = 5

x - y = 4

→ Add the equations to cancel out the y's

2x = 9

→ Divide both sides by 2 to find the value of x

x = 4.5

→ Substitute x = 4.5 back into x - y = 4 to find the value of y

4.5 - y = 4

→ Minus 4.5 from both sides to isolate -y

-y = -0.5

→ Multiply everything by -1

y = 0.5

→ Substitute x = 4.5 and y = 0.5 into x² - y²

4.5² - 0.5² = 20.25 - 0.25 = 20

step-by-step explanation: the answer for wha if rt is 10 centimeters long, and wha is st? it’s 6

the value of x is 9 ⇒ answer b

step-by-step explanation:

* we can solve this problem using cosine and sine rule

- in δ abc

∵ ab = 36 , bc = 28 , ac = 16

- lets find the measure of angle b using the cosine rule

∵ cos b = [ab² + bc² - ac²]/2(ab)(bc)

∴ cos b = [36² + 28² - 16²]/2(36)(28)

∴ cos b = 19/21

∴ m∠b = cos^-1(19/21) ≅ 25°

- lets find the measure of angle a using the sine rule

∵ sina/bc = sinb/ac = sinc/ab

∴ sina/28 = sin25°/16 ⇒ by using cross multiplication

∴ sina = 28 × sin25°/16

∴ sina = 0.7396

∴ m∠a = sin^-1(0.7396) ≅ 48°

- from the figure m∠abd = m∠dbc

∵ m∠abc = 25°

∴ m∠abd = 25°/2 = 12.5°

- in δabd

∵ m∠a = 48° , m∠abd = 12.5°

∵ the sum of the measures of the interior angles of any δ is 180°

∴ m∠adb = 180° - (48° + 12.5°) = 119.5°

∵ ab = 36

∵ ad = x

- use the sine rule to find x

∵ sin∠adb/ab = sin∠abd/x

∴ sin119.5°/36 = sin12.5°/x ⇒ by using cross multiplication

∴ x = 36 × sin12.5°/sin119.5° = 8.95 ≅ 9

* the value of x is 9