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# Complementary

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If x+5 and 4x-15 are complementary angles, find the value of x.

Dec 3, 2018

#4
+1

Complementary angles sum to 90°

x + 5 + 4x - 15 =  90

5x - 10 = 90      add 10 to both sides

5x = 100           divide by 5

x = 20

Credit to CPhill

He is the best

Dec 3, 2018

#1
+2

Complementary angles sum to 90°

x + 5 + 4x - 15 =  90

5x - 10 = 90      add 10 to both sides

5x = 100           divide by 5

x = 20

Thanks to tertre for spotting my stupid error....!!!   Dec 3, 2018
edited by CPhill  Dec 3, 2018
#2
+2

@CPhill, isn't it 5x=100, x=20?

tertre  Dec 3, 2018
#3
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Thanks, tertre....that's what I get for watching football and trying to do math at the same time...I'll make the correction....!!!   CPhill  Dec 3, 2018
#5
+2

Lol! It's okay, I'm watching football, too!

tertre  Dec 3, 2018
#4
+1

Complementary angles sum to 90°

x + 5 + 4x - 15 =  90

5x - 10 = 90      add 10 to both sides

5x = 100           divide by 5

x = 20

Credit to CPhill

He is the best

Guest Dec 3, 2018
#6
-1

Yeah he is!

CoolStuffYT  Dec 3, 2018
#7
-1

If they are complementary angles, then x+5+4x-15=90

5x-10=90

5x=100

x=20

The value of x is 20.

(i was too lazy to do LaTeX lol)

You are very welcome!

:P

Dec 3, 2018