Use the Quadratic Formula To Solve The Equation.
2x^2 - 5x + 7 =0
a. 5/4 + √31/4
b. 5/2 + i√31/2
c. 4/5 + i√62/4
d. 5/4 + i√31/4
-4x^2 + 9x - 8 = 0
a. 9/8 + √47/8
b. 8/9 + i√94/8
c. 9/8 + i√47/8
d. 9/4 + i√47/4
2007-12-18 02:53:19 · 4 answers · asked by x x italian baby x x 1 in Science & Mathematics ➔ Mathematics
OK
2x^2 - 5x + 7 =0
5 +- sqrt(25 - (4)(2)(7)) / 2 (2)
5 +- sqrt(25 -56) /4
5+- sqrt(-31)/4
5/4 +- isqrt31/4 ; Answer D
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-4x^2 + 9x - 8 = 0
-9 +- sqrt(81 - (4)(-4)(-8)) / 2(-4)
-9 +- sqrt(81 - 128) /-8
-9 +- sqrt(-47) /-8
9/8 + isqrt(47)/8; ANswer C
Hope that helps.
2007-12-18 03:17:17 · answer #1 · answered by pyz01 7 · 0⤊ 0⤋
Personally, I prefer just to work it out....
2x^2 - 5x + 7 = 0
2x^2 - 5x = -7
x^2 - 5x/2 = -7/2
x^2 - 5x/4 - 5x/4 + 25/16 = 25/16 - 7/2
x(x - 5/4) - 5/4(4 - 5/4) = 25/16 - 56/16
(x - 5/4) (x - 5/4) = -31/16
(x - 5/4)^2 = -31/16
x - 5/4 = √(-31/16)
x = 5/4 +/- i√31/4
x = answer d (sort of)
-4x^2 + 9x - 8 = 0
-4x^2 + 9x = 8
x^2 -9x/4 = -8/4
x^2 - 9x/8 - 9x/8 + 81/64 = 81/64 - 8/4
x(x - 9/8) - 9/8(x - 9/8) = 81/64 - 128/64
(x - 9/8) (x - 9/8) = -47/64
(x - 9/8)^2 = -47/64
x - 9/8 = √(-47/64)
x = 9/8 +/- i√47/8
x = answer c (sort of)
2007-12-18 03:06:35 · answer #2 · answered by battleship potemkin AM 6 · 0⤊ 0⤋
2x^2 - 5x + 7 =0
x = [5 +/- sqrt(5^2-4(2)(7)]/(2*2)
x = [5 +/- sqrt(-31)]/4
x = 5/4 +/- isqrt(31)/4 {so d is one of the correct answers]
-4x^2 + 9x - 8 = 0
x = [-9 +/- sqrt(9^2-4(-4)(-8))]/(2*-4)
x = [-9 +/- sqrt(-47)]/-8
x = 9/8 +/- isqrt(47/-8 [So c is one of the correct answers]
2007-12-18 03:13:35 · answer #3 · answered by ironduke8159 7 · 0⤊ 0⤋
d
c
2007-12-18 03:01:44 · answer #4 · answered by Anonymous · 0⤊ 0⤋