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# Recent problems solved by 'robertb'

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 Triangles/451483: What is the most condensed formula for the Area of a right triangle if only one angle and the hypotenuse is known?1 solutions Answer 310444 by robertb(4012)   on 2011-05-18 22:20:30 (Show Source): You can put this solution on YOUR website!Let A be the given (acute) angle. Then the side adjacent to angle A will have length c*cosA, where c is the length of the hypotenuse. Then the area of the right triangle is then
 absolute-value/451489: If the function g is defined for all nonzero numbers y by g(y)=y/absolute value y what is the value of g(2)-g(-200)?1 solutions Answer 310435 by robertb(4012)   on 2011-05-18 22:03:26 (Show Source): You can put this solution on YOUR website! ==>
 Circles/451444: The measure of an angle is formed by two tangents to a circle of 90 degrees. If the radius of the circle is 8 centimeters, how far is the vertex of the angle from the center of the circle?1 solutions Answer 310416 by robertb(4012)   on 2011-05-18 20:52:24 (Show Source): You can put this solution on YOUR website!The intersection point of the two lines, the two points of tangency, and the center of the circle, would form the vertices of a square. The radius being 8 cm means the side of the square is 8 cm. The distance from the vertex of the angle to the center of the circle is then equal to the length of the diagonal of the square, which is cm.
 Mixture_Word_Problems/451451: A 30 ml solution of alcohol and water is 10% alcohol. How much water must be added to result in a 5% solution?1 solutions Answer 310411 by robertb(4012)   on 2011-05-18 20:45:11 (Show Source): You can put this solution on YOUR website!0.10*30 + 0.00*w = 0.05*(30 + w) ==> 3 = 1.5 + 0.05w ==> 1.5 = 0.05w ==> w = 30 ml of water must be added.
 Square-cubic-other-roots/451436: Complete the empty space to make a true statement. 5√2 - √___ + √2 = 4√21 solutions Answer 310409 by robertb(4012)   on 2011-05-18 20:42:49 (Show Source): You can put this solution on YOUR website! ==> ==> ==> x = 8.
 Linear_Equations_And_Systems_Word_Problems/450999: a number consist of two digits whose sum is 9.If 27 is subtracted form the number. Its digits are reversed1 solutions Answer 310209 by robertb(4012)   on 2011-05-18 03:41:32 (Show Source): You can put this solution on YOUR website!let the tens digit be x, y the ones digit. Then x+ y = 9, and 10x + y - 27 = 10y + x. The second equation is equivalent to 9x - 9y = 27, or x - y = 3. Combining this with the first equation, we get x = 6, and y = 3. The original number is 63.
 Distributive-associative-commutative-properties/451006: Give a counterexample to show that each of the following generalizations about the set of integers is false: a. Closure property for division b. Distributive property for division over addition c. Commutative property for division d. Associative property for division e. Associative property for subtraction f. Commutative property for subtraction Thank you! 1 solutions Answer 310207 by robertb(4012)   on 2011-05-18 03:18:08 (Show Source): You can put this solution on YOUR website!a. -6/5, a division of two integers, does not produce an integer. b. , not an integer. c. d. , while , hence e. (1-2)-3 = -1 - 3 = -4, whereas 1-(2-3) = 1--1 = 2. f. 4-7 = -3, whereas 7-4 = 3.
 Sequences-and-series/451065: 32-26=6 9-3=6 11-5=6 ???-8=6 ???=141 solutions Answer 310206 by robertb(4012)   on 2011-05-18 03:08:21 (Show Source): You can put this solution on YOUR website!5*3 - 1 = 14
 test/451078: What is the ref abgle of 100 degrees? How can you tell which quadrant its in? I guessed Q1 and got 80 as an answer.. is this wrong? If so how do I fix it? Thanks!1 solutions Answer 310204 by robertb(4012)   on 2011-05-18 03:00:25 (Show Source): You can put this solution on YOUR website!The angle in standard position measuring 100 degrees has terminal side in Quadrant 2, while its reference angle is 80 degrees. Yes, the reference angle of -220 degrees is 40 degrees.
 test/451075: Is the sin of -3pi/4 = -sqrt2/2 or is it not negative?1 solutions Answer 310203 by robertb(4012)   on 2011-05-18 02:55:57 (Show Source): You can put this solution on YOUR website!If the angle is expressed in radians, then indeed .
 test/451076: What is tan of -3pi/4? I got 1..1 solutions Answer 310202 by robertb(4012)   on 2011-05-18 02:54:32 (Show Source): You can put this solution on YOUR website!If the angle is in radians, then indeed .
 Sequences-and-series/450317: For the geometric series: 8+2+1/2+1/8+... find S1,S2,S3,S4 and S5. I alread found that S1=8, S2=10, S3=10 1/2, but I need S4 and S5. I also need to use these sums to approximate S. Then I need to use the Infinite Geometric Series formula, which is S=S1/r-1, to find S. S1= 8, because its the first number in the series R= the common ratio, which I don't know 1 solutions Answer 310201 by robertb(4012)   on 2011-05-18 02:48:47 (Show Source): You can put this solution on YOUR website! The formula for the sum of an infinite geometric series is , where -1 < r <1. Here r = 1/4. Hence
 Quadratic_Equations/450405: Factor the polynomial by grouping the terms together two at a time. x3 - 6x2 - 4x + 24 Please show me the steps to get the answer. Thanks1 solutions Answer 310200 by robertb(4012)   on 2011-05-18 02:35:47 (Show Source):
 Linear-systems/450366: solve by elimination a - 2b = -3 -2a + 4b = 6 1 solutions Answer 310199 by robertb(4012)   on 2011-05-18 02:33:04 (Show Source): You can put this solution on YOUR website!Multiplying the top equation by -2 gives exactly the bottom equation, hence the system is dependent. The solution set is the set of all points (a, b), where .
 Quadratic-relations-and-conic-sections/450257: find the foci of the hyperbola having the equation 4y^2-x^2=161 solutions Answer 310198 by robertb(4012)   on 2011-05-18 02:19:56 (Show Source): You can put this solution on YOUR website!The center of the hyperbola is the point (0,0). The transverse axis is the y-axis. Now for the hyperbola, , or , or , or . The foci are (0,) and (0,-).
 Trigonometry-basics/450913: i'm confused on trying to find out what this equals.. the problem is 4^x-2^x-12=01 solutions Answer 310197 by robertb(4012)   on 2011-05-18 02:15:01 (Show Source): You can put this solution on YOUR website! <==> <==> <==> , or The second equation has no real solutions, and so, , or , or x = 2.
 Quadratic_Equations/450979: Solve: 2x^2=-x+10 Please show me the steps to get the answer. Thanks1 solutions Answer 310196 by robertb(4012)   on 2011-05-18 01:51:36 (Show Source): You can put this solution on YOUR website! ==> ==> ==> x = -5/2, 2
 Word_Problems_With_Coins/450986: an unbiased coin is tossed 5 times. what is the probability the coin lands heads more than once1 solutions Answer 310195 by robertb(4012)   on 2011-05-18 01:48:18 (Show Source):
 Polynomials-and-rational-expressions/451025: What Is The Property Illustrated Of -34.9+0=-34.9 1 solutions Answer 310194 by robertb(4012)   on 2011-05-18 01:45:16 (Show Source): You can put this solution on YOUR website!Additive Identity (or Zero) Property
 Polynomials-and-rational-expressions/451023: What Is The Property Illustrated of 2k+(-2k)= 0 1 solutions Answer 310192 by robertb(4012)   on 2011-05-18 01:39:10 (Show Source): You can put this solution on YOUR website!Additive Inverse property
 Quadratic_Equations/451039: FIND THE STANDARD EQUATION OF ANY PARABOLA THAT HAS VERTEX V. V(4, -2) 1 solutions Answer 310191 by robertb(4012)   on 2011-05-18 01:36:29 (Show Source): You can put this solution on YOUR website!Either , or , where a is a non-zero arbitrary constant.
 Functions/451041: if x be real , then the maximum value of 5+4x-4xsquare will be equel to1 solutions Answer 310190 by robertb(4012)   on 2011-05-18 01:29:49 (Show Source):
 Equations/451057: write the equation of a line containing the given point and perpendicular to the given line. (4,-8); 4x+7y=5 The equation of the line is Y=1 solutions Answer 310189 by robertb(4012)   on 2011-05-18 01:25:58 (Show Source): You can put this solution on YOUR website!The equation of the line must take the form 7x - 4y = c, where c is an undetermined coefficient. To find c, use the coordinates of the given point. 7*4 - 4*(-8) = 28 + 32 = 60. Hence the equation is 7x - 4y = 60.
 logarithm/451052: (Log_a(8)/(Log_a (4) 1 solutions Answer 310187 by robertb(4012)   on 2011-05-18 01:21:14 (Show Source):
 Rational-functions/450989: Write an equation in standard form for each circle. (0,0), radius 3 (0,2), radius 8 (5, –1), radius 6 1 solutions Answer 310132 by robertb(4012)   on 2011-05-17 22:03:44 (Show Source):
 Exponential-and-logarithmic-functions/450944: If log9=0.95 and log2=0.30, then what is log8?1 solutions Answer 310127 by robertb(4012)   on 2011-05-17 21:57:07 (Show Source):
 Quadratic-relations-and-conic-sections/450970: Find the standard equation of a hyperbola when you're given this equation : x^2 - 4y^2 - 28x - 24y + 156 = 01 solutions Answer 310123 by robertb(4012)   on 2011-05-17 21:53:45 (Show Source):
 Evaluation_Word_Problems/450945: The ratio of two numbers is 5:7. If 6 is added to each number, the ratio of the numbers is 7:9. What are the numbers?1 solutions Answer 310119 by robertb(4012)   on 2011-05-17 21:46:53 (Show Source): You can put this solution on YOUR website! ==> ==> ==> ==> 45(x+6) = 7(7x + 30) 45x + 270 = 49x + 210 60 = 4x x = 15. ==> y = 21.
 Graphs/450958: find the equation for the line having a slope = 3/4 & a x-intercept of -2. put answer in the form y=mx+b.1 solutions Answer 310115 by robertb(4012)   on 2011-05-17 21:37:58 (Show Source): You can put this solution on YOUR website!The line contains the point (-2,0), which is the x-intercept. ==> ==> ==> b = 3/2 ==> the equation of the line is
 Exponential-and-logarithmic-functions/450967: simplify log 10^9+ 10 ^ log91 solutions Answer 310110 by robertb(4012)   on 2011-05-17 21:29:17 (Show Source):