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Help me with unsolveable problems?
This is my second go with College Algebra. I am a junior in college going to school on a financial aid program that only covers me a limited number of classes so I cannot keep re-taking this class. We use a computer program for all homework and the 'help me solve this' button isn't helping. here are the last problems from Chapter 1 that I can't figure out. Someone please solve these for me..
1.) 2x2 - 3x - 35 = 0
x=_______ (smaller value)
x=_______ (larger value) I got -5/2 as smaller value and 7 as larger value.
2.) Use the quadratic formula to solve the equation.
5x(x + 9) = -65
x=_____ (smaller value)
x=______ (larger value) I got -9/2 and -5/2
3.) Change the equation to quadratic form and solve it by the most efficient method.
x − 2 = 8/x (the 8 is 8 over x)
x=_____ (smaller value)
x=_____ (larger value) (even the textbook did not have an example to teach me how)
4.) Change the equation to quadratic form and solve it by the most efficient method.
1/x-1 + 1/x-5 = 3/8
x= _____ (smaller value)
x= ______ (larger value)
5.) Change the equation to quadratic form and solve it by the most efficient method.
29/b - 23 = -22/b+1
x= _____ (smaller value)
x= ______ (larger value)
Thank you so much. If you guys can solve these 5, I will make about a B.
the 2x2 in number 1 is 2x squared
5 Answers
- QCLv 79 years agoFavorite Answer
To denote powers use ^, i.e. x squared = x^2, x cubed = x^3, etc...
2x^2 - 3x - 35 = 0
2x^2 - 10x + 7x - 35 = 0
2x (x - 5) + 7 (x - 5)
(2x + 7) (x - 5) = 0
x = -7/2
x = 5
It looks like you got the 2 coefficient in the wrong factor
-------------------------------
2.
5x(x + 9) = -65
x (x + 9) = -13
x^2 + 9x + 13 = 0
x = (-9 ± √(81 - 4(1)(13))) / 2
x = (-9 ± √(81-52)) / 2
x = (-9 ± √29) / 2
Smaller value: (-9 - √29)/2
Larger value: (-9 + √29)/2
-------------------------------
3.
I'm not exactly sure what sort of example you expected.
Have you never been showed how to cross-multiply, to get rid of denominators?
(x - 2) = 8/x
x (x - 2) = 8
x^2 - 2x - 8 = 0
(x + 2) (x - 4) = 0
x = -2
x = 4
-------------------------------
4.
This time instead of cross-multiplying, we'll just multiply both sides by least common denominator
1/(x-1) + 1/(x-5) = 3/8
Multiply both sides by lcd = 8(x-1)(x-5)
8(x-1)(x-5)/(x-1) + 8(x-1)(x-5)/(x-5) = 8(x-1)(x-5) * 3/8
8(x-5) + 8(x-1) = 3(x-1)(x-5)
8x - 40 + 8x - 8 = 3 (x^2 - 6x + 5)
16x - 48 = 3x^2 - 18x + 15
0 = 3x^2 - 18x + 15 - 16x + 48
3x^2 - 34x + 63 = 0
3x^2 - 27x - 7x + 63 = 0
3x (x - 9) - 7 (x - 9) = 0
(3x - 7) (x - 9) = 0
x = 7/3
x = 9
-------------------------------
5.
29/b - 23 = -22/(b+1)
Multiply both sides by b(b+1)
29(b+1) - 23b(b+1) = -22b
29b + 29 - 23b^2 - 23b = -22b
-23b^2 + 6b + 29 = -22b
-23b^2 + 28b + 29 = 0
23b^2 - 28b - 29 = 0
b = (28 ± √(784 - 4(23)(-29))) / 46
b = (28 ± √(784 + 2668)) / 46
b = (28 ± √3452) / 46
b = (28 ± 2√863) / 46
b = (14 − √863) / 23
b = (14 + √863) / 23
Mαthmφm
- JayLv 59 years ago
1) 2x²-3x-35 = 0
(2x+7)(x-5) = 0
x = -7/2 = smaller value, 5 = larger value
2) 5x(x+9) = -65
5x²+45x = -65
5x²+45x+65=0
x²+9x+13 = 0
x = (-9±√29)/2 = (-9-√29)/2 = smaller value, (-9+√29)/2 = larger value
3) x-2 = 8/x
x(x-2) = 8
x²-2x-8 = 0
(x-4)(x+2) = 0
x = 4 = larger value, -2 = smaller value
4) 1/(x-1) + 1/(x-5) = 3/8
[(x-5)+(x-1)]/(x-1)(x-5) = 3/8
(2x-6)/(x-1)(x-5) = 3/8
8(2x-6) = 3(x-1)(x-5)
16x-48 = 3(x²-6x+5)
16x-48 = 3x²-18x+15
0 = 3x²-34x+63
0 = (3x-7)(x-9)
x = 7/3 = smaller value, 9 = larger value
5) 29/b - 23 = -22/(b+1)
(29-23b)/b = -22/(b+1)
(29-23b)(b+1) = -22b
6b-23b²-29 = -22b
-23b²+28b-29 = 0
23b²-28b+29 = 0
x = (28±i√1884)/46 = (28-i√1884)/46 = smaller value, (28+i√1884)/46 = larger value
- Anonymous9 years ago
Q1
2x^2 -3x -35=0
(2x+7)(x-5)=0 ........... (check you get factorisation correct by multiplying it back out!)
x=-7/2 or x=5
Q2
to use formula must be in form
ax^2 + bx+ c
5x^2 +45x +65 =0
a=5, b=45 c=65
gives -9 plusminus root29 all over 2
Q3
multiply everything by x to remove the "over x"
x(x-2)=8
x^2 -2x -8=0
then solve as normal
Q4
as above but first multiply by (x-1) and then by (x-5). Simplify as needed, rearrange as solve as normal
Q5
similar but replaced the x's with b's
- Anonymous9 years ago
3/
x(x-2)=8
x^2 - 2x - 8 = 0
(x-4)(x+2)=0 ---> x = 4 or -2
4/
LCD = (x-1)(x-5)
8(x-5)+8(x-1) = 3(x-1)(x-5)
expand , simplify then solve for x
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