# Posts by Reiny

Total # Posts: 39,548

**Math**

Nothing to solve, just multiply the two numbers. (Do 3 x 67, you should be able to do that in your head, then move the decimal 3 places to the left.) Of course you could also use your calculator.

**Math**

The way you typed it : 5^x + 2•5^x+1 = 3*5^x + 1 it does not factor over the rational numbers Secondly you did not say what type of number x is, let's assume x is a whole number, that is x = 0, 1, 2, 3, ... if you meant: 5^x + 2*5^(x+1) = 5^x( 1 + 2(5^1) ) = 5^x ( 11...

**Math**

first term --- a second term ---- ar a - ar = 2 a(1-r) = 2 sum to infinity = 15 a/(1-r) = 15 [a(1-r)][a/(1-r)] = 2(15) a^2 = 30 a = ± ?30 from a = ar+2 ?30 = ?30r + 2 r = (?30 - 2)/?30 = 1 - 2/?30 so we have ?30, ?30 + 2 , .... sum(5) = a (r^5 - 1)/(r-1) = .... = ..... ...

**math**

when it hits the ground, h = 0 0 = -4.9x^2 + 21.3x 4.9x^2 - 21.3x = 0 x(4.9x - 21.3) = 0 x = 0 , which corresponds to the moment she kicks the ball or x = 21.3/4.9 = appr 4.4 seconds

**Math**

I guess you could form columns for "n" and "left side" n ... LS 0 3 1 9 2 15 --- getting too big, looking for 2 on RS -1 -3 ---- too low, so n is between 0 and -1 1/2 6 ---- too high -1/2 -3 --- too low so between 0 and -1/2 -1/4 3/2 ----- too low so ...

**math**

notice that each new term is -3 times its previous, or tn = -3t(n-1) so we have -4, 12, -36, 108, -324

**Algenra 1**

both correct

**math**

This is the same type as your other post. Only this time you don't add anybody not belonging to either set.

**Calculus**

Do you actually expect somebody to do this assignment for you?

**MATH**

No, the 5 that do both are counted in the 16 geography students, AND the 18 chemistry students, so you are counting them twice number of students = 16+18 - 5 + 3 = .... make a Venn diagram to see.

**Math**

10(x+27) ? 26

**Math**

You will have to count the number of days from Feb 12 to June 23, I will leave that up to you and label it 'days' in I = PRT, your I = 40, R = ??, T = days/365 , P = 2000 40 = 2000(R)(days/365) R = 40(365)/(2000(days)) = your R will be a decimal, I will assume you know...

**pre-calculus math**

a zero of 3 gives us a factor of (x-3) complex zeros always come in conjugate pairs, so if -3-2i is one of them, -3+2i must be another. factors are (x - (-3-2i)) and (x - (-3+2i)) or (x + 3 + 2i) and (x + 3 - 2i) multiply the last two to get a quadratic factor (......) your f(...

**Math**

Thanks Steve, how sloppy of me

**Math**

amount of the 1% stuff to be added ---- x ounces .1x + .4(100) = .16(x + 100) solve for x

**Algebra**

f(2) = 21 , you had that f(a) = 6a^2 - 3 all you had to do is find the average rate of change, or more commonly known as the slope average rate of change = (6a^2 - 3 - 21)/(a - 2) = (6a^2 - 24)/(a-2) = 6(a^2 - 4)/(a-2) = 6(a+2)(a-2)/(a-2) = 6(a+2) , a ? 2

**Math**

1.6666666667 is NOT an irrational number. (1.6666666667 = 16666666667/10000000000 , there! I wrote it as a rational number)

**Calculus**

Your equation should have been h = -16t^2 - 6t + 130 When it hits the ground, h = 0 so, 16t^2 + 6t - 130 = 0 I would use the quadratic equation formula to solve for t (to be able to handle this topic, you MUST know that formula) make sure to reject any negative value of t.

**Math**

PV = 30,000 + 30,000( 1 - 1.0593^-12)/.0593 = ....

**alg**

y = 3x - 1 for (2,5) LS = 5 RS = 3(2) - 1 = 5

**Algebra**

I just googled : graph of a quadratic function, and guess what ? replace "quadratic" with the other two words

**Advanced Algebra**

I agree, but then pay this off as quickly as possible with such a high interest rate. Notice the payment of $25 wouldn't even pay the interest. (first months interest after introductory period = 1800(.2399)(1/12) = $35.99

**1 Out Of 100 Math Trick HELP PLEASE!!!**

1. Choose a number between 1 and 100. ------> x 2. Multiply the number by 5. -------> 5x 3. Add 15 to the number. -------> 5x+15 4. Divide the number by 5. ------> x+3 5. Subtract the original number. ------> 3 try it with any number: 1. ----- 12 2. ------ 60 3...

**Pre-calc**

Use brackets to write the fractions, such as 1/(2x) + 6/2 , <---- that was a guess, I can't tell what you meant

**Pre-calc**

I will assume that these are the zeros or the solutions to your function = 0 if 3-i is a zero, then 3+i is a zero, since complex solutions always appear in conjugate pairs sum of those roots = 6 product of those roots = 9 - i^2 = 10 so the quadratic producing those two complex...

**Algebra**

your formula is interpreted this way f(3) = f(2) + f(1) f(4) = f(3) + f(2) f(5) = f(4) + f(3) etc so f(3) = 3 + 2 = 5 f(4) = ....... notice we already eliminated b) continue .... btw, this is a famous sequence called the Fibonacci sequence, one of my favourite topics in Math.

**Math**

How did you possible get those answers ???

**Algebra**

What problem? Are you switching names ??

**Algebra**

No How did you get that ????

**Math**

remember , Perimeter = 2 x width + 2 x length area = length x width Perimeter = 2(5x-4) + 2(5x) = .... area = 5x(5x-4) = ... in each case simplify my expression

**Pre-Calculus**

To prove an identity, we usually start with one side and using basic identities show that it is equal to the other side LS = cosx - sex = cosx - 1/cosx = (cos^2 x - 1)/cosx = - sin^2 x / cosx = -sinx(sinx/cosx) = -sinx tanx = RS

**Math**

Didn't you want to make at least $200 ? So it should be 15h ? 200 h ? 40/3 , not less than like you had However, your conclusion that the painter must work a minimum of 13 and 1/3 hours to earn at least $200, is correct

**Math**

correct,

**Algebra 2**

depends on the transformation. e.g. suppose we have f: (x,y) ----> (x,-y) , a reflection in the x-axis , and g: (x,y) ---> (-x,-y) , a reflection in the origin if we do fg (x,y) ---> (x,-y) ---> (-x,y) and if we do gf (x,y) = (-x,-y) ---> (-x,y) , we get the ...

**math**

explain the meaning of 127nine

**algebra**

| 4x - 5 | > 4 4x - 5 > 4 OR -4x + 5 > 4 4x > 9 or -4x > -1 x > 9/4 or x < 1/4 change into the notation you learned and graph on a number line

**algebra 2**

6x-8 = 4 or -6x+8 = 4 6x = 12 or -6x = -4 x = 2 or x = 2/3

**algebra**

follow the same steps and procedure as in https://www.jiskha.com/display.cgi?id=1506548306 except use AND between the two inequations

**algebra 2**

width --- x length --- 2x perimeter = 2width + 2 lengths = 54 continue

**algebra**

Both conditions are referenced in terms of nickels, so let the number of nickels be x number of dimes = x+1 number of pennies = x+6 Value equation: 5x + 10(x+1) + x+6 = 480 continue ....

**Algebra 2 A**

correct make sure your equation is 26.00+3.25x=24.00+3.50x

**maths**

Ummmhh, if you are half as old as your sister, wouldn't your sister be twice as old?? . I defined it the way I did to avoid fractions. What does 6(x-20) mean? Does it not say 6 times (the son's age) ?? 2x-20 = 6(x-20) 2x-20 = 6x - 120 -4x = -100 x = 25 So the son is ...

**maths**

So the father is now twice as old as his son son's age ---- x father's age ---- 2x Twenty years ago : son's age = x-20 father's age = 2x-20 2x-20 = 6(x-20) solve for x, etc

**math**

first of all , you have a typo in g(x)=x^2=7x I think you meant: g(x)=x^2+7x , since the + and the = are on the same key you are given that g(x) = x^2 + 7x so you want g(3). As Philip stated, wherever you had an x , now put in a 3 g(3) = 3^2 + 7(3) = 9 + 21 = 90 so since f(x...

**College Algebra: Please Help Me. Thanks.**

f(x)=4x^2+3x+5 and g(x)=3x^2+2x+2 I will do A and C, you do the rest a) (f+g)----> 7x^2 + 5x + 7 (f+g)(3) = 7(3)^2 + 5(3) + 7 = 63 + 15 + 7 = 85 c) (f-g)(x) = 4x^2+3x+5 - (3x^2+2x+2) = x^2 + x + 3

**Math**

a) h = 8 + 6t 6t = h-8 t = (h-8)/6 c) when t = 6 h = 8 + 6(6) = .... d) when h = 29 29 = 8 + 6t 21 = 6t t = 21/6 = 3.5 it would take 3.5 months

**PRE-CALC**

you are given that x = i is a solution Complex roots, just like irrational roots, always come in conjugate pairs, so x = -i is another solution so you know (x+i) and (x-i) are factors (x+1)(x-1) = x^2 + 1 which means x^2 + 1 is factor of your given polynomial now do a long ...

**8th grade Math Connections Academy**

#5 25 is a perfect square ---- 5^2 = 25 , but 27 is a perfect cube --- 3^3 = 27 #6 is incorrect ?9 - 7 = 3-7 = -4, which is an integer Whole numbers are positive integers I agree with the others.

**Math**

24.4 trillion = 24,400,000,000,000 cost per person = 24,400,000,000,000/325,000,000 = 24,400,000/325 = $62,769 At $62 it could be paid off in 1 year by everybody chipping in a bit, unfortunately .....

**Math**

number dogs = 135(.365)(1.6) = appr 78.8 million dogs

**math**

-8y+3(g+h) - -5y-4(g+h) = -8y + 3g + 3h + 5y - 4g - 4h = ..... btw, - - 5 is considered "poor mathematical form"

**Maths**

I drew a horizontal flight path 400 m above the ground. On that path, I labeled the first position of the plane as A and the 2nd position as B, and the location of Melbourne on the ground as M I also labeled C on the flight path as the point directly above M. Let the speed of ...

**math**

3150 = 9*25*14 you take it from here

**9th Grade Math**

yes

**9th Grade Math**

none are correct A typical equation of a straight line, other than vertical or horizontal lines, need an x and a y variable. I will do one of them , say #4, you do the others slope of line = (-10-2)/(15-5) = -12/10 = -6/5 using the point (5,2), y - 2 = (-6/5)(x-5) multiply ...

**Calculus**

Let the vertex on the line 3x + 4y = 12 be (x,y) then y = (12-3x)/4 = 3- 3x/4 area = xy = x(3 - 3x/4) = 3x - 3x^2 /4 d(area)/dx = 3 - (3/2)x = 0 for a max of area (3/2)x = 3 3x = 6 x = 2 , y = 3 - 6/4 = 3/2 max area = xy = 2(3/2) = 3 units^2

**math Please help!!**

look at your list of properties, which pattern do you see?

**math Please help!!**

one has square brackets around it, and the other one doesn't. I would consider both to be -3

**algebra**

each of the equal angles ---- x third angle = 2x - 4 so : x + x + 2x-4 = 180 continue

**Algebra**

now: son's age --- x man's age --- 3x 5 years ago: son's age = x-5 man's age = 3x-5 3x-5 = 4(x-5) solve and the mystery will be unravelled.

**math**

just solve the two equations. I would use y = 20-x from the first and sub it into the 2nd let me know what you get

**math**

Here is just one such worksheet http://www.bearsdenacademy.e-dunbarton.sch.uk/_includes/attachments/P1283/Unit2_TrigonometricEquations.pdf That should keep you busy for a while. Try the questions before looking at the solutions.

**math**

Your first source would be your textbook. Perhaps your teacher gave you a handout of such equations. You can always google "trig equations" or "trig equations worksheet" There would be an infinite number of such equations.

**maths**

time in car ---- t hrs time on motorcycle --- 1 - t hrs 30t + 18(1 - t) = 22 solve for t, sub into 30t to get the distance in km

**Math**

width --- w length --- 3w 2(w+3w) = 96 4w = 48 w = 12 m or 1200 cm 3w = 36 m or 3600 cm area of flower bed = 1200(3600) cm^2 area of rectangle including path = (1280)(3680) cm^2 area of walkway = the difference or 390400 cm^2 volume of concrete needed for walk = 390400(15) cm^...

**algebra**

5x - 3y = 0 5x = 3y or 3y = 5x y = (5/3)x , which is in the form of y = mx, a direct variation.

**Math**

The areas of two similar figures area proportional to the square of their corresponding sides, so w^2/18^2 = 52/117 w^2 = 144 w = ?144 = 12

**Physics/Math**

You must be studying vectors in 3-D and cos ?, cos ?, and cos ? must be the direction cosines of a vector <a, b, c> you will recall that cos ? = a/?(a^2 + b^2 + c^2) cos ? = b/?(a^2 + b^2 + c^2) cos ? = c/?(a^2 + b^2 + c^2) Here is a great youtube which uses a specific ...

**maths**

What happened to the 100 ml that were split ? If they were given as part of the share , why not just do 2500 ml ÷ 4 = 625 ml per child or 100 ml ÷4 = 25 ml remaining 2400 ml ÷ 4 = 600 ml, and of course 600 ml + 25 ml = 625 ml , same as above

**Math**

Where are points a and b on the pond? What is a mosese ?

**Further maths**

Let x be the number who passed both. x + 31-x + 29-x + 3 = 50 -x = -13 x = 13 number who passed Chemistry only = 31-x = 31-13 = 18

**Math**

In most languages, there are special words for very common numerical values, as well as mathematical concepts e.g. almost every language has a special word for 12 besides the numerical name. That is, in English we use "dozen" meaning 12, in German "Dutzend"...

**math**

translating your conditions: W = k * w* h^2 / l given: w = 3in, h = 4in, l = 6 ft or 72 in , W = 28 tons 28 = k(3)(16)/72 k = 42 W = 42 * w* h^2 / l plugging in the second case: W = 42(5)(16)/240 = 14 tons

**Algebra 2**

6|6-4x|=8x+4 divide by 6 |6-4x|=(8x+4)/6 ---- I wanted to isolate the absolute value expression 6-4x = (8x+4)/6 OR 6-4x = -(8x+4)/6 36-24x = 8x+4 or 36-24x = -8x - 4 -32x = -32 or -16x = -40 x = 1 or x = 40/16 = 5/2 I will leave it up to you to verify my answers

**Math**

can you think of a number which divides into 42 as well as 49 ???

**Math**

Just add and subtract in base 2 x + 1011 + 1101 = 11101 x + 11000 = 11101 = 101 or , copping out and changing to base 10 10112 = 1110 11012 = 1310 111012 = 2910 y + 11 + 13 = 29 y = 5 and 510 = 1012 , as above

**Algebra 2**

#3, you list no choices, but the question itself is your answer: r ? 1/5 the rest are correct up to #7

**Math**

draw a dotted line y = 4x+2, (your line is to be excluded) and shade in the region below the line 2x - y ? 2 -y ? -2x + 2 y ? 2x - 2 draw a solid line y = 2x-2, and shade in the regions below it your solution is the intersection of the 2 regions

**algebra**

correct, how did you get that? I am more interested in your method and thinking than the actual answer.

**Algebra**

I don't see where it wants the number of hours only. I see "how long will it take ....." your answer of 55.3846... is correct so that would be 55 hours and .3846... of an hour so .3846..(60) = 23.0769... minutes if you wanted it broken down into seconds, use the ...

**Algebra**

I answered this for you 4 days ago. Why are you asking the same question again ?? https://www.jiskha.com/display.cgi?id=1505894047

**stats**

one letter variable ---- 26 two character variable ----- 26x36 three character variable --- 26 x 36 x 36 four character variable ---- 26 x 36 x 36 x 36 = 26(36)^3 ... eight character variable ---- 26(36)^7 Possible characters = sum of the above = 26(1 + 36 + 36^2 + ... + 36^7...

**Math**

larger --- x smaller = (1/2)x middle = (3/4)x x + x/2 + 3x/4 = 126 times 4 4x + 2x + 3x = 504 x = 56 larger is 56, smallest is 28 , middle is 42

**Math**

number of advanced tickets ---- x number of at door tickets ----- 480-x 4x + 5(480-x) = 2100 solve for x

**math**

Is the "discount" confusing you ? I believe most textbooks would handle it like this: Let the annual discount rate be i 1-i = (1 - .005)^12 = .995^12 = .94162 i = .058377 or a discount of 5.8377% Had it been just plain old interest ..... let the nominal rate be i (1+...

**Algebra**

f(x)={x^2, if x ? -4 {x^3, if -4 < x ? 1 {?x, if x > 1 so if x = -4, it belongs to the first function f(-4) = (-4)^2 = 16 if x = 4, we have the last function f(4) = ?4 = 2

**Mathematics**

"where t is the time in hours from....." is incomplete Did you mean from noon ? Let's assume it is after noon, else make the necessary adjustments at 9:45 pm , t = 9.75 set your calculator to radians d = 3.163 metres The min of 3cos 30t is -3 and its max is +3 So...

**Math**

cost of gift ---- x cost for each of the nine originals = x/9 cost per student with 13 paying = x/13 x/9 - x/13 = 33.32/9 times 117 13x - 9x = 3898.44 4x = 3898.44 x = 974.61 check: original share = 974.61/9 = 108.29 new share = 974.61/13 = 74.97 saving per share = 33.32 , as ...

**Math**

number of skiers --- x number of boarders ---- 2x , notice x : 2x = 1 : 2 2x - x = 1250 etc

**math**

Han's starting number ------ x , counts backwards by 100 Sally's starting number ----- 300 counts forward by 10 after 6 counts, Sally is 360 after 6 counts, Han's is at x - 600 x - 600 = 360 x = 960

**Algebra**

let the number of 50 notes be 3x let the number of 20 notes be 5x , notice they are in 3:5 ratio number of 10 notes = 25 - 3x - 5x or 25 - 8x value of notes equation: 50(3x) + 20(5x) + 10(25-8x) = 590 150x + 100x + 250 - 80x = 590 170x = 340 x = 2 sub back into my definitions

**Algebra**

let the amount of aluminum added be x kg .55(160) + x = .7(160+x) 88 + .55x + x = 112 + .7x .85x = 24 x = appr 28.24 kg

**Math**

a+2d = -1 a+6d = 11 subtract them: 4d = 12 d = 3 from a+2d = -1 , a = -7 term(n) = a+(n-1)d = -7 + 3(n-1) = -7 + 3n - 3 = 3n - 10 "the numbers of which must be added to get a sum of 430" I will assume you mean, "how many terms are needed to have sum of 430"...

**Algebra**

follow the same steps I showed you in your previous question.

**Algebra**

speed of jet in still air ---- x mph speed of wind ---- y mph 4(x+y) = 1008 ---> x+y = 252 4(x-y) = 832 ----> x-y = 208 add them: 2x = 460 x = 230 from x+y = 252 , y = 22

**College Algebra**

let the time taken to catch up be t hours distance covered by the sister be 65t distance covered by Sarah is 60(t+2) but the went the same distance, so ... 65t = 60(t+2) solve for t

**Algebra**

let the smallest angle be x then the next smallest angle is 3x+26 You know in a right-angled triangle the two smaller angles must add up to 90° , so x + 3x+26 = 90 solve for x ....

**Math medication problems**

One confusion that could arise is to use cc vs ml http://thecompounder.com/2015/04/13/cc-vs-ml-whats-the-difference/ the ordered rate was 600 cc/8 hours = 75 cc/hour The pharmacist erroneously calculated this to be 200 ml/hr or 200 cc/hr

**Algrebra**

your slope for BD should have been 9/1 or 9 To be a rhombus, the slopes of the diagonals should have been negative reciprocals of each other the negative reciprocal of -1/5 would be +5 which it isn't. so ABCD is not a rhombus Another way to check: The sides are not equal ...

**math**

Just translate into Math "three consecutive numbers" ---> x, x+1, x+2 "the sum of the second and the third numbers " --- x+1 + x+2 "exceeds the first by 14" ---> x+1 + x+2 - x = 14 now just solve for x, and sub back into my definitions