is this completing the square or what....because my math teacher want give me a clue since he doesnt know his self....last time he marked my answer wrong and didnt have any clarification on why it was wrong
2007-02-18 08:06:39 · 13 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
*Set the equation to "0" --- subtract 80 from both sides (when you move a term to the opposite side, always use the opposite sign).
3x^2 + 5 - 80 = 80 - 80
3x^2 + 5 - 80 = 0
3x^2 - 75 = 0
Sec: factor the expression - find the greatest common factor.
3(x^2 - 25) = 0
3(x + 5)(x - 5) = 0
Third: solve the "x" variables - set both parenthesis to zero.
1. x + 5 = 0
*ISolate "x" on one side - subtract 5 from both sides.
x + 5 - 5 = 0 - 5
x = 0 - 5
x = - 5
2. x - 5 = 0
*ISolate "x" on one side - add 5 with both sides.
x - 5 + 5 = 0 + 5
x = 0 + 5
x = 5
Solutions: 5, -5
2007-02-18 09:10:04 · answer #1 · answered by ♪♥Annie♥♪ 6 · 2⤊ 0⤋
a rapid examine exhibits that the discriminant b² - 4ac < 0 this suggests the roots are complicated. 3x² - 5x = -7 Dividing by utilizing 3 x² - 5x/3 = -7/3 polishing off the sq. (x - 5/6)² - 25/36 = -7/3 (x - 5/6)² = -7/3 + 25/36 (x - 5/6)² = -fifty 9/36 x - 5/6 = ±?(-fifty 9/36) x - 5/6 = ±(?fifty 9/6)i the place i = ?-one million so x = 5/6 + (?fifty 9/6)i and x = 5/6 - (?fifty 9/6)i or x = (5 + ?fifty 9)i / 6 and x = (5 - ?fifty 9)i / 6 EDIT : i'm assuming that 3x2 potential 3x² ( thrice x squared).
2016-12-18 06:04:22 · answer #2 · answered by ? 4 · 0⤊ 0⤋
You don't need completing the square
3x^2 + 5 = 80 sub 5
3x^2 = 75 divide by 3
x^2 = 25 Take sqrt and get
x = pos or neg 5
2007-02-18 08:13:30 · answer #3 · answered by lizzie 3 · 1⤊ 0⤋
3x^2 + 5 = 80? subtract 5 from both sides
3x^2 = 75 divide both sides by 3
x^2 = 25 take the square root of both sides
x=5
2007-02-18 08:11:36 · answer #4 · answered by crippledsonic 1 · 1⤊ 1⤋
All of the previous answers are almost right. Remember that when you take the square route of anything it is positive or negative 5, not just 5.
Answers: 5,-5
2007-02-18 08:17:48 · answer #5 · answered by buttercup 3 · 1⤊ 0⤋
Subtract 5 from both sides:
3x^2=75
Divide 3 from both sides:
x^2=25
Square both sides:
√x^2=±√25
x=±5
Check:
3(-5)^2+5=80
3(25)+5=80
75+5=80
80=80
3(5)^2+5=80
3(25)+5=80
75+5=80
80=80
I hope this helps and good luck with your class!
2007-02-18 09:30:22 · answer #6 · answered by Anonymous · 0⤊ 0⤋
3x^2 + 5 = 80
3x^2 = 75
x^2 = 25
sq.rt. x = sq.rt. 25
x=5
2007-02-18 08:14:27 · answer #7 · answered by Christie 3 · 1⤊ 1⤋
80 - 5 = 3X^2
75 = 3x^2
25 = x^2
x = 5, -5
2007-02-18 08:10:16 · answer #8 · answered by Flaming Pope 4 · 1⤊ 0⤋
3x^2=75
x^2=25
x=5
2007-02-18 08:17:33 · answer #9 · answered by surmy 2 · 1⤊ 1⤋
that equation is not quadratic.
to solve...
3x^2 = 75
x^2 = 25
x = 5
2007-02-18 08:11:27 · answer #10 · answered by microbio 1 · 1⤊ 1⤋