# Posts by Reiny

Total # Posts: 38,061

**9th grade algebra (completing square)**

You seem to have a good grasp of doing these. I verified most of your answers by subbing them back into the original equation. All the ones I tried were correct. I suggest you take your calculator and test your answers.

*November 9, 2016*

**correction - math**

Y = 2x^2 + 3?x is NOT a function, since a quadratic must have the form y = ax^2 + bx + c that is, the exponents of the x term can only be 2 or 1 the term ?x is x^(1/2) Furthermore, the graph of a quadratic function is a parabola, the graph of Y = 2x^2 + 3?x looks like this, ...

*November 9, 2016*

**Math**

Since no condition is stated, that number would be C(9,5) or 126 There seems to be something missing here.

*November 9, 2016*

**pre calc**

amount = a (1/2)^(t/k), where k is the half-life period when t = 2, amount = .7a .7a = a(1/2)(2/k) .7 = (.5)^(2/k) take log of both sides and use log rules log .7 = (2/k)log .5 2/k = log .7 / log .5 = .514573... k = 2/.514573.. = 3.887 days the half-life is 3.89 days check: ...

*November 8, 2016*

**Math HELP HELP**

x^2+4x-41 = x^2+4x + 4 - 4 - 41 = (x+2)^2 - 45 expand and simplify to verify my answer

*November 8, 2016*

**pre calc**

N = a (2)^(t/20), where N is the number of bacteria, t is the number of minutes, a is the initial count, our problem. counting 7:00 as zero time and 5:00 am as t = 10 hrs = 120 minutes 1000000 = a(2)^(120/20) 1000000 = a(2)^6 64a = 1000000 a = 1000000/64 = 15625 of the germs ...

*November 8, 2016*

**Math**

Did you even look at the solution I gave you here http://www.jiskha.com/display.cgi?id=1478637677 This is the same type of problem. btw, the denominator on the right side factors to (x+3)(x-1)

*November 8, 2016*

**Algebra**

"j vaires directly with m and inversely with p" ----> j = km/p plug in the given, and solve for k

*November 8, 2016*

**MATH**

Your second equation IS a quadratic function. since the highest power you see is x^2. Sorry if you misunderstood. btw, don't say "square root of x", that would be ?x the term is "x squared"

*November 8, 2016*

**MATH**

Small change to your definition. The highest power must be a square term. The degree of a polynomial is determined by the highest power, so in your case you would have a cubic because of the x^3 term a quadratic must have the form y = ax^2 + bx + c, where the a,b, and c are ...

*November 8, 2016*

**Math**

I will assume you meant: 2x/(x+1) + 3/(5x+5) = 0 the whole thing falls apart when the denominators are zero, since then we would be dividing by zero When does that happen? when x+1 = 0 x = -1 and 5x+5 = 0 5x = -5 x = -1 so x ? -1

*November 8, 2016*

**Math**

Look up the definition of a function in your text or in your notes. In a nutshell, it says that for every x there is one and only one y value So, if you see two or more y values for the same x, then it is NOT a function e.g. in the first I see (5,2) and (5,10) , so NOT a ...

*November 8, 2016*

**Calculas-Differentiation**

I have now done 2 of your quite straightforward questions. You MUST know how to do these type of relatively easy Calculus problems. Show me the steps of your solution so I can check it.

*November 8, 2016*

**Calculas-Differentiation**

The line y=1/4x+1 has a slope of 1/4 So the perpendicular has a slope of -4 y = 6 - x^2 dy/dx = -2x set -2x = -4 , and solve, then use your grade 9 method of finding the equation of the tangent

*November 8, 2016*

**Algebra**

amount of the 20% stuff ---- x gallons amount of the other stuff ---- 700-x .2x +.3(700-x) = .24(700) solve for x to reveal the mystery.

*November 8, 2016*

**Calculas-Differentiation**

dA/dt = 6t + 1/5 plug in t = 2 for dA/dt

*November 8, 2016*

**trigonometry- hight and distance**

At 45° the length of the shadow will also be h m

*November 8, 2016*

**Math**

x+y=16 x-y=3 just add them, to find x subtract them to get y

*November 8, 2016*

**Algebra**

in its standard form , at centre (0,0) a^2 = b^2 + c^2 4^2 = b^2 + 2^2 b^2 = 12 x^2 / 16 + y^2 / 12 = 1

*November 7, 2016*

**Math**

If you are picking just one student, prob(boy) = 12/29

*November 7, 2016*

**Math**

why not try it with something like (x+4)(2x-1) expand it and see how many products you have before simplifying

*November 7, 2016*

**Math**

to have an undefined slope, the line must be a vertical line. A vertical line has the form x = c, where c is a constant look at our point, its x value is -3 so the equation of your line is x = -3

*November 7, 2016*

**math**

radish seeds --- x pumpkins ----- x+6 x + x+6 + 40 = 80 solve for x

*November 7, 2016*

**correction - Math**

forget my previous post, did not notice the x^3 f(x)=4x^2-2x+3 ; g(x)=2x^3+4x-7 (f-g)(x) = 4x^2 - 6x + 10 - 2x^3 (f-g)(2) = 16 - 12 + 10 - 16 = -2 bobpursley was correct

*November 7, 2016*

**Math**

3rd one: f(x)=4x^2-2x+3 ; g(x)=2x^3+4x-7 (f-g)(x) = 2x^2 - 6x + 10 (f-g)(2) = 8 - 12 + 10 = 6

*November 7, 2016*

**Math**

let's take $100 interest earned = 100/9 let the rate be r then the number of years = r 100(r/100)(r) = 100/9 r^2 = 100/9 r = 10/3 = 3 1/3 % for 3 1/3 years in general: amount invested --- x interest earned ---- x/9 rate ----- y/100 time ---- y I = PRT x(y/100)(y) = x/9 y^2...

*November 7, 2016*

**math last question asap ples :P**

Well, for A, is 36 + 9 = 64 ?? or , is 6^2 + 3^2 = 8^2 ?? for B, is 144 + 25 = 169 ?? or, is 12^2 + 5^2 = 13^2 ?? btw, just because one of these statements is true, does not "prove" the Pythagorean Theorem, it merely illustrates it.

*November 7, 2016*

**math**

difference of squares 16s^2 - 9 = (4s+3)(4s-3)

*November 7, 2016*

**MATH ..can you guys help??? also ASAP :p**

simply look what happened to the x and y. It should be clear that (x,y) ----> (x-5, y + 8)

*November 7, 2016*

**stats**

prob(right) = 1/4 prob(wrong) = 3/4 prob(at least 15 right) = prob(15 right) + prob(16 right) + ... + prob(40 right) or = 1 - (prob(none right) + prob(1 right) + prob(2 right) + ...+prob(14 right) I hope you have lots of patience and don't make any errors. I will do one of...

*November 7, 2016*

**math**

I assume that you mean: "Luis rides his bicycle 3/4 of a mile in 5 minutes" Since 5 minutes is 1/12 of an hour, like you stated rate = distance/time = (3/4) / (1/12) mph = 9 mph

*November 7, 2016*

**pre-calc.**

ln(100) = ln(10^2) = 2ln10 so ln100/ln10 = 2ln10/ln10 = 2

*November 7, 2016*

**Pre-Calc**

cot x = 1/2 can be written in an infinite number of ways, the 1/2 is simply the ratio expressed in simplest form how about cot x = .5/1 or how about cotx = .378/.756 etc by definition cotx = adjacent side/opposite side in a right-angled triangle so in the original given cotx...

*November 7, 2016*

**Math**

x^2 + 2^2 = 5^2 solve for x

*November 7, 2016*

**If y= (2x + 2)^3 find dy/dx using chains rule**

I would just do it in one step dy/dx = 2(2x+3)^2 (2) = 4(2x+3)^2 using the steps asked for: let u = 2x+2 du/dx = 2 then y = u^3 dy/du = 3u^2 dy/dx = (dy/du)(du/dx) = (3u^2)(2) = 4u^2 = 4(2x+2)^2 Once you see the pattern of these type of derivatives, you should be able to ...

*November 7, 2016*

**Algebra 2**

two consecutive even integers ---> x and x+2 x + x+2 ? 130 2x ? 128 x ? 64 so how about 62 and 64 as the largest pair

*November 7, 2016*

**Math**

3 + 6*4 + 3

*November 7, 2016*

**Math**

I recognize this to be an circle. Do you want it in standard form? if so, then ... 8x+x^2-2y=64-y^2 x^2 + 8x + ... + y^2 - 2y + ... = 64 complete the square x^2 + 8x + 16 + y^2 - 2y + 1 = 64 + 16 + 1 (x + 4)^2 + (y-1)^2 = 81 centre is (-4,1), radius is 9

*November 7, 2016*

**Calculas**

Steve did this for you http://www.jiskha.com/display.cgi?id=1478532807 Why are you reposting?

*November 7, 2016*

**math**

the middle term of the expansion is term(10) term(10) = C(20,9)(1)^11 x^9 = 167960x^9 the 9th term is C(20,8) x^8 = 125970x^8 the 12 term is C(20,11) x^11 = 167960x^11 geometric mean = ?(125970(167960)x^19) 167960x^9 = ?(125970(167960)x^19) 167960x^9 = ?(125970(167960))*x^9 ?x...

*November 7, 2016*

**math**

Now: Patty ---- x years Sam ----- 4x next year: Patty = x+1 Sam = 4x + 1 4x+1 = 3(x+1) continue

*November 7, 2016*

**math**

lw = 24 2l + 2w = 20 l+w = 10 l = 10-w in lw = 24 (10-w)(w) = 24 10w - w^2 = 24 w^2 - 10w + 24 = 0 (w-6)(w-4) = 0 w = 6 , then l = 4 w = 4 , then l = 6

*November 7, 2016*

**Calculas**

nothing to see here

*November 7, 2016*

**math**

one angle ---- x the other ----- (2/3)x or 2x/3 2(x+2x/3) = 360 2x + 4x/3 = 360 carry on

*November 7, 2016*

**maths**

" ... the sum of the first five terms is one-fourth of the next terms." confusing, I will assume you meant: the sum of the first five terms is one-fourth of the next term. i.e. the sum of the first five terms is one-fourth of the 6th terms. a = 2 6th term = a+5d sum(...

*November 7, 2016*

**Math**

width ---- x length ---- 3x - 1 2x + 2(3x-1) = 40 carry on

*November 7, 2016*

**math**

(5/6)x + 3.60 = 4.35

*November 7, 2016*

**Finance**

i = .12 n = 50-18 = 32 amount = 1500( 1.12^32 - 1)/.01 = $457,271.58 where can you get 12% these days?

*November 7, 2016*

**trig help**

cosec40(sin40+sin80+cos120) = (1/sin40)(sin40 + sin80 + cos120) = 1 + sin80/sin40 + cos120/sin40 = 1 + 2sin40cos40/sin40 -1/(2sin40) = 1 + 2cos40 - (1/2)csc40

*November 7, 2016*

**algebra**

D^2 = 10^2 + 7^2 = 149 D = ?149 = appr 12 , to the nearest whole number

*November 7, 2016*

**maths**

width --- x length ---- 3x 2(x+3x) = 1.6 km 8x = 1600 m x = 200 then 3x = 600 The field is 200 m by 600 m for an area of 120,000 m^2

*November 7, 2016*

**@ Joshua - maths**

I also have seen this question now for the third time. I also keep ignoring it since it can't be answered with the information given. Include me in the "bad attitude" category.

*November 7, 2016*

**MATH**

what is 25000(1 + .0485/4)^24 ?

*November 6, 2016*

**Math**

yup, you are right. Need a third cup of coffee. I agree that the question makes no sense.

*November 6, 2016*

**Math**

The exterior angles of any polygon add up to 360° so: 3x+2x+4x = 360 x = 40

*November 6, 2016*

**Mathe**

I agree with appr 2.83 m but you would round that to 3 m , not 2 m since A and C have no units, I suspect a typo, and one of those was 3 m

*November 6, 2016*

**@ nms, Algrebra readiness**

It said " the negative square root of 7" ---> -?7 not " the square root of negative 7" ---> ?-7

*November 6, 2016*

**Algrebra readiness**

the negative square root of 7= appr -2.6 so to the nearest integer that would be -3 None of your choices given match that ???? #2 If each square is 2 by 2 ft, its area is 4 ft^2 and 30 of them would give us 120 ft^2 --> we need 170 If each square is 3 by 3 ft, its area is 9...

*November 6, 2016*

**maths**

Thanks nms for catching my error I used 2/3 instead of 1/3 (I must have looked back at the wrong fraction)

*November 6, 2016*

**maths**

rate of pipe A = 1/15 rate of pipe B = 1/10 combined rate = 1/6 amount done after 4 minutes = 4(1/6) = 2/3 so 1/3 is left to be done time using only A = (2/3) / (1/15) = 10 minutes

*November 6, 2016*

**Math-Trigo**

It said "without a calculator" All the work following is done in my head. sinA = -12/13 = y/r x^2 + y^2 = r^2 x^2 + (-12)^2 = 13^2 x^2 + 144 = 169 x^2 = 25 x = ± 5 , but A is in quad IV, so x = 5 so sinA = -12/13, cosA = +5/13 tanA = (-12/13) / (5/13) = -12/5 ...

*November 6, 2016*

**trig**

Did you make your sketch? On mine I let Jane's distance to the tower's base be x m, and Bill's distance to the tower be y m There are two right-angled triangles For Jane: tan70° = 34/x x = 34/tan70° do the same step for Bill's distance add x and y

*November 6, 2016*

**Maths**

My diagram: A vertical line PQ, to show the tower, P at ground-level Another vertical AB, the points of observation with A at ground-level let AP = x draw a horizontal from B to meet PQ at R in triangle APQ tan 60 = (h+40)/x x = (h+40)/tan60 in triangle BRQ tan30 = h/x x = h/...

*November 6, 2016*

**Calculus**

u • v = |u| |v|cosØ, where Ø is the angle between them -4 -21 = ?50 ?25 cosØ -25 = 25?2cosØ cosØ = -1/?2 Ø = 135°

*November 5, 2016*

**Pre-Calculus**

(u • v)(u + v) = (-4-21)(<3,4>) = -25<3,4> = <-75, -100>

*November 5, 2016*

**maths**

2x=3x subtract 2x from both sides 0 = x

*November 5, 2016*

**Algebra 2**

not familiar with your notation does log(30,8) mean log30 8 ?

*November 5, 2016*

**algebra**

V = kt/p for the given data: 20 = k(350)/35 k = 20(35)/350 = 2 V = 2t/p when t=330, p=30 V = 2(330)/30 = 22

*November 5, 2016*

**MATH**

"y varies inversely with x" ---> y = k(1/x) y = 8 when x = 5 8 = k/5 k = 40 so : y = 40/x plug in x=2, and find y

*November 5, 2016*

**Adv function**

I suspect a typo http://www.wolframalpha.com/input/?i=Cos%5E4(x)%2Bsin%5E4(4)%3Dcos(2x) notice the graph of the left side does not intersect the graph of the right side

*November 5, 2016*

**Algebra**

a) depends on how you define your variables e.g. let the time be t hours, and the distance be d miles then : d = kt plug in d= 180 and t = 4.5 to solve for k rewrite the equation , now that you know k sub in d = 320 and solve for t

*November 5, 2016*

**Mathe**

number of way to have a sum of 4: 13 22 31 number of ways to have a sum of 6: 15 24 33 42 51 prob(sum of 4 OR sum of 6) = 8/36 = 2/9

*November 5, 2016*

**Calculus**

Since you are in Calculus, I assume you know the area of a triangle is (1/2) ab sinØ, where Ø is the contained angle between a and b A = (1/2)(4)(4)sinØ A = 8sinØ dA/dØ = 8cosØ for a max of A, 8cosØ = 0 Ø = 90° or 270...

*November 5, 2016*

**Arithmetic**

add up the 3 costs, then divide by 3

*November 5, 2016*

**Arithmetic**

value of original stock = 75(50) = 3750 after increase of 8%, the value is 3750(1.08) = 4050 number of shares = 4050/50 = 81

*November 5, 2016*

**Math**

If I recall, a gross is defined to be 144 so they bought 6(144) or 864 pencils at a weekly use of 24 pencils, the number of weeks = 864/24 or 36

*November 5, 2016*

**math**

total profit = 6200-4000 = 2200 number of bikes at $50 profit per bike = 2200/50 = 44

*November 5, 2016*

**math**

done later this morning

*November 5, 2016*

**Algebra**

7?9 + 5(8-3) = 7(3) + 5(5) = 21 + 25 = 46

*November 4, 2016*

**tri**

make a sketch distance along first direction = 5 hrs x 23 knots = 115 n miles distance along 2nd direction = 6(23) = 138 n miles angle between the two directions = 150° by cosine law: x^2 = 115^2 + 138^2 - 2(115)(138)cos 150° = 59756.64... x = 244.45 nautical miles = ...

*November 4, 2016*

**Adv function**

"I can't get the l.s to equal r.s" If you are trying to show that it is an identity, good luck , since it is not (try it with 30° for x) So I will assume you are solving: (2-sin^2x)/-sinx=sinx 2 - sin^2 x = -sin^2 x 2 = 0 , which is a contradiction, there is ...

*November 4, 2016*

**math- Trigonometry**

I recognize .8641 as an approximation to ?3/2 if cos x = ?3/2 x = 30° sin30° = 1/2 or .5 using your .8641 sinx = .5033

*November 4, 2016*

**algebra 1**

or a line parallel to y = 5x - 2 is y = 5x + b , but (8,-2) lies on it -2 = 40 + b b = -42 y = 5x - 42

*November 4, 2016*

**geometry**

no idea where A, B, C, D, and O are Cannot be answered as is.

*November 4, 2016*

**Math**

selling price = .75(172.36) final price after tax = (1.09)(.75)(172.36) = ...

*November 4, 2016*

**Math**

Oh, dear, I think a ban for D&B is certainly due.

*November 4, 2016*

**Tricky Math Question**

0^0 is undefined reason: 0^n = 0 for any value of n but a^0 = 1 for any value of a so we have a contradiction, which drives mathematicians crazy, thus it is undefined my 25 year old calculator gives me an error message for 0^0

*November 4, 2016*

**Mathematics**

15 > 7 - t/3 The method for solving in-equations is the same as that for solving equation, except: when you multiply or divide by a negative number, you must reverse the inequality sign add t/3 to both sides t/3 + 15 > 7 subtract 15 from both sides t/3 > -8 multiply ...

*November 4, 2016*

**Math**

profit = 75 percentage profit = 75/300 = .25 or 25%

*November 4, 2016*

**Math**

Repost using proper English.

*November 4, 2016*

**@ anridas - Maths**

Please don't post a question as an answer to somebody else's posting. the square numbers less than 144 are 121, 100, 81, 64, 49, 36, 25, 16, 9, 4, 1 ... looks like 16 and 9 are it. since 16 x 9 = 144 or: 144 = 4 x 4 x 3 x 3 = 4^2 x 3^2 = 16(9)

*November 4, 2016*

**Maths**

since 1/10 + 2/3 + 1/7 < 1 , there have to be other colours, and yes, it is possible 1/10 + 2/3 + 1/7 = 191/210 minimum counters is 210 191/210 = x/1000 210x = 191000 x = 909.5 but we have to round down since we can't have partial counter, so 909 counters

*November 4, 2016*

**Math**

add: 2 1/5 + (1/2)(2 1/5) + (7/8)(2 1/5) = 11/5 + (1/2)(11/5) + (7/8)(11/5) = 11/5 + 11/10 + 77/40 take over, the LCD is 40

*November 4, 2016*

**Algebra**

let the certain amount of 8% stuff be x oz .5(8) + .08x = .32(8+x) solve for x

*November 4, 2016*

**mathematics**

poorly worded question. We only "solve" equations, you don't have an equation. I will assume you meant: m^2 + 6m + 7 = 0 m^2 + 6m + .... = -7 + ..... m^2 + 6m + 9 = -7 + 9 (m+3)^2 = 2 m+3 = ± ?2 m = -3 ± ?2

*November 4, 2016*

**Maths**

so .75x = 8400 x = 8400/.75 = .... "wold" ----> would

*November 4, 2016*

**Math**

Bar model??? standard way: Ryan ----- x cans Anne ----- x/2 cans Joel ------ 2x cans x + x/2 + 2x = 1925 (7/2)x = 1925 x = 550 take over

*November 4, 2016*

**Maths.**

You don't need a "×" symbol to show multiplication. Use brackets or * or standard algebraic notation e.g. 3×x^2×y ---> 3(x^2)(y) or simply 3x^2 y Furthermore, you will need brackets to eliminate any ambiguity I read yours as: 3x^2 y + (5/8)x^...

*November 4, 2016*

**math**

1800 mm = 180 cm = 1.8 m Consider 1 ha as 100 m by 100 m Assume the plough does swaths of 1.8 m up and down. 100/1.8 = 500/9 runs each 100 m long have to be ploughed total distance = (500/9)(100) m time = distance/rate = (500/9)(100) m / 7 km/h = (500/9)(100) m / 7000 m/h = ....

*November 4, 2016*

**Maths**

51 = 1+50 = 2 + 49 ... = 50+1 there are 50 such cases out of 50(50) so prob = 50/(50*50) = 1/50 55 , the smallest we can start with is 5 55 = 5 + 50 = 6 + 49 .. = 50 + 5 ----> 46 of them prob = 46/2500 = 23/1250

*November 4, 2016*