x2 + y2 = 13 where y = 2?

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

Update:

Answer:

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

8 Answers

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  • Tasm
    Lv 6
    9 years ago

    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

    Answer X = 3

  • 9 years ago

    x2 + y2 = 13 where y =2

    therefore x2 + 4 = 13

    x2 = 13-4

    x2 = 9

    x = sq root of 9 which is 3

    Answer x =3 (c)

  • ?
    Lv 7
    9 years ago

    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

  • 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)

  • 9 years ago

    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

  • 9 years ago

    x² + y² = 13

    x² + 2² = 13

    x² + 4 = 13

    x² = 13-4 =9

    x²=9

    x=±√(3)= ±3

    So the answer is c.

  • 9 years ago

    x2 + 4 = 13

    x2 = 9

    x = square root of 9

    x = 3

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