# x2 + y2 = 13 where y = 2?

how do i figure this out. thank everone for helping me!!!

Update:

a. 2

b. 9

c. 3

d. 2.5

hey, i got 4.5 also but it isnt an option

Update 2:

the correct answer was b. i dont get it but it said b

Relevance
• X2 + y2 = 13 where y = 2?

X2 + (2)2 = 13

X2 + 4 = 13

X2 = 13 - 4

X2 = 9

X = srt(9) = plus or minus 3

(-3)2 + (2)2 does not equal 13

(3)2 + (2)2 = 13

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• x2 + y2 = 13 where y =2

therefore x2 + 4 = 13

x2 = 13-4

x2 = 9

x = sq root of 9 which is 3

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• For:

x^2 + y^2 = 13,

... substituting y = 2:

x^2 + 2^2 = 13

=>

x^2 + 4 = 13

=>

x^2 = 9

=>

x = ±√9

=>

x = ±3

So, x = -3 or x = 3

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• Anonymous
9 years ago

x^2 + y^2 = 13

sub y = 2

x^2 + 2^2 = 13

x^2 = 13-4

x^2 = 9

x= +3 / -3

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• x^2 + y^2 = 13

substitute 2 in:

x^2 + 2^2 = 13

x^2 + 4 = 13

x^2 = 9

x= 3 (c)

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• x^2 + y^2 = 13

y=2

x^2 +(2)^2 =13

x^2 +4 =13

x^2 = 13 -4

x^2 = 9

square root on both sides

x = sqrt (9)

x = 3

C

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• x² + y² = 13

x² + 2² = 13

x² + 4 = 13

x² = 13-4 =9

x²=9

x=±√(3)= ±3

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