# Posts by steve

Total # Posts: 51,710

**Algebra**

well, 5^(2x) = (5^2)^x = 25^x so, what do you think?

**math**

----1 = 1 draw the number line place a closed circle (dot) at 1 shade to the left

**Algebra**

I assume you mean x/(x-2) + (x-1)/(x+1) = -1 using a common denominator of (x-2)(x+1), we have x(x+1) + (x-1)(x-2) = -1(x-2)(x+1) 3x(x-1) = 0 x = 0 or 1

**Math pls**

plot the two points. The slope is the change in y divided by the change in x. y changes from 2 to -2 x changes from 6 to 4 so, the slope is (-2-2)/(4-6) = -4/-2 = 2

**Algebra check answers?**

the slope is (5+2)/(-3+4) = 7, not 1/7 so, using the point-slope form, y+2 = 7(x+4) work with that. 4 1/6 = 25/6 As written, none matches. ?64 = 8

**Math - Please help ASAP!**

#1 Nope. 2*5-3 ? -7 #2 Nope. 1 ? -4(7)+3 In fact, I suspect a typo. None of the choices works.

**Maths**

did this for you last night. see related questions below.

**Algebra 2**

since the lowest value of cos(x) is -1. the lowest temperature is 3.8(-1)+2.2 = -1.6

**Math**

a negative times a negative is positive. So, (-7)(-12) = 7*12 I'm sure you can manage that ...

**math**

If the shadow length is s, and the height is h, then h = ks That means that h/s = k, a constant. So, you want s such that 6/15 = 20/s

**math**

huh? Just add them up!

**maths**

draw a diagram. It should be clear that tan? = 65/42

**Math**

what, no cubits, chains or roods?

**math - eh?**

There seems to be some context missing. You want to clarify things a bit?

**Math**

heck - just set the two equal: -x^2+9 = 3/x x^3-9x+3 = 0 cubics usually require a numeric or graphical method. I assume you have studied some of those. http://www.wolframalpha.com/input/?i=x%5E3-9x%2B3%3D0

**Math**

clearly t= 7508.4 i think is not a reasonable answer. 7500 years? 300 e^(5k) = 1500 e^(5k) = 5 5k = ln5 k = ln5/5 = 0.32 so, y(t) = 300 e^(0.32t) y(10) = 300 e^3.2 = 7360 300 e^(0.32t) = 12500 e^(0.32t) = 41.67 0.32t = ln 41.67 = 3.73 t = 3.73/0.32 = 11.65

**Math**

find k using 300 e^(5k) = 1500 use that k with t=10 finally, use that k to find t when 300 e^(kt) = 12500

**math**

50lb = 22.73kg so, you will need 1.5*22.73 = 34.1 mg . . .

**science**

150 mi/hr * 1609 m/mi * 1hr/3600s = 67 m/s

**Maths - Matrices**

oops - misspoke: A-1 = 1/2 (1 2) (1 4) So, X = (0 0) (4 4) see http://www.wolframalpha.com/input/?i=(inverse+%7B%7B4,-2%7D,%7B-1,1%7D%7D)*(2%7B%7B-4,-4%7D,%7B2,2%7D%7D)

**Maths - Matrices**

If you write this as AX = B then X = A-1B A-1 = (1 1) (1 2) now just crank it out.

**Science**

of what?

**Maths**

630 = 2^4•3•13+6 940 = 2^3•3^2•13+4 so, your number is 2^3•3•13 = 312 630 = 2*312+6 940 = 3*312+4

**math**

no, (a) has a negative slope. Rearrange things into slope-intercept form and you get 5x + y = 50 y = -5x+50 slope = -5, intercept=50 do that for the others, and it will then be clear which is what you want.

**math**

first step: which have positive slopes?

**Algebra**

you want to try that without TeX? x^n - 1/x^n = p(x - 1/x) ... where does z come in?

**Algebra**

google is your friend: https://math.stackexchange.com/questions/1967491/suppose-we-have-the-following-identity-px-1-py2-ax2-bxy-cy2-f

**Algebra**

xf(x) + f(1-x) = x(x-1)(x+1) (1-x)f(1-x) + f(1-(1-x)) = (1-x)((1-x)-1)(1-x+1) multiply the first by (1-x): x(1-x)f(x) + (1-x)f(1-x) = x(x-1)(x+1)(1-x) f(x) + (1-x)f(1-x) = (1-x)(-x)(2-x) subtract to get (x(1-x)-1)f(x) = (x(x-1)(x+1)(1-x))-((1-x)(-x)(2-x)) f(x) = -x(1-x)(x^2-x+...

**Algebra**

If y=f(x) maps a value of x to a value of y, then look at the first line. It says f(4) = -2 f(4) = 2 it cannot be both. So, (A) is not a function.

**Algebra**

if a value of x maps to two different y's, it is not a function. So, look for a line with a repeated 1st element.

**Algebra**

ya think? 3f(1/x)+(2f(x)/x)=x^2 now, if x = -2, 3f(-1/2) + 2f(-2)/-2 = 4 3f(-1/2) - f(-2) = 4 if x = -1/2, 3f(-2)+2f(-1/2)/(-1/2) = 1/4 -4f(-1/2) + 3f(-2) = 1/4 f(-2) = 67/20 ------------------------ or, we have ------------------------ 3f(1/x)+2(1/x)f(x) = x^2 3f(x) + 2xf(1/x...

**physics**

conserve momentum: 3*5 + 4*0 = 3*0 + 4v

**Math**

The number of fish in a tank decreases by x% each year. Given that the number of fish halves in 8 years, (1-x/100)^t = (1/2)^(t/8) t log(1-x/100) = t/8 log(1/2) log(1-x/100) = log(2^(-1/8)) 1 - x/100 = 2^(-1/8) x/100 = 1 - 2^(-1/8) x = 100(1 - 2^(-1/8)) = 8.3

**Math Help TIMED!**

but yes, it is A.

**Algebra 2**

not quite... 5?8^(4x) = 376 8^(4x) = 75.2 4x log8 = log75.2 x = log75.2/(4log8) or, since 4log8 = log4096, x = log409675.2

**math**

you are correct. The question is, why did you use that value? Just think it through, and you should see why it is correct.

**Chemistry**

start by recalling that 1 mole occupies 22.4L (dm^3) at STP Then use the fact that PV=kT since all the items are given in the same units, the formula works just fine. Just find the one which matches the standard values.

**trigonometry**

is the building uphill or downhill from the post? If the building is downhill from the post, at a horizontal distance of x, then let a = vertical distance from the base of the building to the base of the post x = horizontal distance between building and post h = height of post...

**trigonometry**

Draw a diagram. Let a = distance from A to the base of the tower b = distance from B to the base of the tower h = height of the tower Then we have b^2 = a^2+50^2 h/b = tan18° h/a = tan30° Now you can find a,b and thus h.

**Science**

google is your friend: https://socratic.org/questions/write-a-balanced-ionic-equation-to-represent-the-reaction-between-sulfur-dioxide

**Maths**

clearly, (7 1/4)*(1 3/5) = 29/4 * 8/5 = ?

**Math**

42%

**Math**

no idea what "M<mon" means

**Trigonometry**

yes

**Trigonometry**

just so.

**Trigonometry**

just recall the definition of the trig functions, in terms of a standard triangle. sin = y/r cos = x/r tan = y/x since r is always positive, you just need to ask yourself where are x and y both positive? do you feel lucky? . . . well, do ya?

**calc**

in either case, apply the chain rule. If u is a function of x, then if y is a function of u, we have dy/dx = dy/du * du/dx so, what do you get?

**math**

they will be in QII and QIII. cos 53.3° = 0.5982 Use that for your reference angle.

**Maths - Polar coordinates**

you can also do the rotation simply by adjusting the angle. Rotate (?13,30) by 30, and you end up at (?13,60). Now just convert that back to rectangular coordinates.

**physics**

Draw right triangle ABC with right angle at A. As sides of the triangle, a^2 = b^2+c^2 a^2 = 12^2 + (18-a)^2 a = 13 You have a 5-12-13 triangle.

**Maths**

you really need to proofread your posts ... The cross-section is a trapezoid with area A = (3/2 + 3)/2 * 15 m^2 So, the volume of the pool is A*40 m^3 now just convert that figure to "lotelres"

**MATH**

how many of the 6 numbers are greater than 3?

**Physics**

Draw the velocity vector v, pointing kind of northwest, with length 100. At its end, add a vector pointing eastward, of length 45. You want to figure the angle of the velocity vector so that when you add the two, the east-west component is zero. That is, the resultant velocity...

**Math**

h/7.5 = sin32°

**Algebra 2**

x chose option 2 x+45 chose option 1 the rest (475-x-(x+45)) chose neither now add up all the money 35(x+45)+25x+15(430-2x) = 13275 solve for x and then you're on your way.

**Math**

(c) two line with different slopes intersect in a single point, so ...

**math**

since the curved part is a semi-circle of radius 4, (8*6 + ?/2 * 4^2)*15 = 720+120? in^3

**Algebra 2**

x = (g-5)^2 g-5 = ±?x g = 5±?x picking one branch, g = 5+?x Hard to say what all your weird syntax means.

**Math**

the plane z = k is parallel to the x-y plane at a distance |k| The x-y plane is the plane z=0 (which, or course, does pass through the origin)

**cms**

y+x = 116 y-x = 24 Now just solve for x,y and 180-(x+y)

**Maths**

area grows by a factor of 1.2^2 = 1.44 resistance decreases by that factor. (Not a decrease of 44% !!)

**math**

217 = 7*31 310 = 10*31 713 = 23*31 It appears that dividing any of the original numbers by 31 will leave a remainder of 3.

**Maths**

sides

**math**

just add the two numbers. That's what "increase" means.

**physics**

(90-27)g / 50ml = 63/50 g/cm^3 now just convert that to kg/m^3

**Math**

7m + (m/2)(d-7)

**Algebra**

your equations are correct your solution is correct D is of course, not a solution. Not only does 5*180+8(-30)?900, but -30 is not a valid number of tickets.

**fractions**

7600(3/8)(2/3)

**geometry**

? * 0.5^2 * 3 (1+8+27) = 27? in^3

**Math**

#1 ok #2 not so much what is -3-4 ?

**Algebra 2 quick check**

except for the typos, looks good. Online you should use parens or spaces so we can tell whether 3/4x means 3/(4x) or 3/4 x = (3/4)x

**Algebra 2**

I disagree: 4600*0.983^7 = 4080

**Algebra**

you seriously need to work on your formatting... http://www.jiskha.com/display.cgi?id=1496332774

**Math**

just as with the others, the sum is a1/(1-r) just plug in your numbers.

**Math A Calculus**

this is calculus. Surely you can work with fractions... (a) a+b = (2/3)+(-1/4) = 8/12-3/12 = 5/12 (b) what do you think? recall that the length of ai+bj+ck = ?(a^2+b^2+c^2)

**Math**

so, what are the even multiples of 13? 26 52 78 so, what do you think?

**Math**

convert each displacement to rectangular form, and then just add them up. Then if the final position is (x,y), the displacement is ?(x^2+y^2)

**Math**

no diagrams here.

**maths**

well, 100% is all of the students. what is 100-54? no idea what the "strength" of a class is. Size? If so, then 23 = (1-.54)x

**geometry**

so, using the formulas, what do you get?

**Math (Sorta dumb question)**

Your final answer is correct.

**Math**

a1=243 r = 2/3 an = 243(2/3)^(n-1) a5 = 48 s = a/(1-r) = 5/(5/4) = 4

**Math**

hard to say, with no figure to compare ...

**Math**

recall that sin(90-?) = cos? cos(90-?) = sin? now see what you have.

**Algebra 1b**

(d) not (a) if n is negative

**Math**

huh? You surely must see from Scott's lines of text that 792 = 12C5

**Math**

oops tan(?) = y/x

**Math**

well, let's try to take this step by step. Let's call the two lower vertices L and R. Suppose we have L = (h,-k) Then the line LC has slope mLC = k/(1-h) and its equation (using point A) is y = k/(1-h) (x-1) Since LRC is equilateral, its angles are all ?/3. So, the ...

**Math**

well, let's try to take this step by step. Let's call the two lower vertices L and R. Suppose we have L = (h,-k) Then the line LC has slope mLC = k/(1-h) and its equation (using point A) is y = k/(1-h) (x-1) Since LRC is equilateral, its angles are all ?/3. So, the ...

**Math**

well, let's try to take this step by step. Let's call the two lower vertices L and R. Suppose we have ?/3 L = (h,-k) Then the line LC has slope mLC = k/(1-h) y+k = k/(1-h) (x-h) Since LRC is equilateral, its angles are all ?/3. So, the slope of LR is mLR = tan(arctan(...

**Calculus**

clearly, the series converges, since |sin(4n/?)+3|/4^n < |1+3|/4^n which converges to 16/3 But I can't come up with the actual limit value.

**Math: Trigonometry**

not quite -- 4/?7 is csc? did you draw the triangle?

**Math**

just set up equations to fit the facts. For example, #1 m/k = 5/6 m = k-12 so, (k-12)/k = 5/6 #2 7/15 = f/75 d = 75-f what do you get for the others?

**Math**

(c) because multiplying or dividing by a negative value changes the direction of the inequality 6 > 3 6(-4) = -24 < -12 = 3(-4)

**Math**

You know that Pn = 5+7n so, replace n with 4, and you get P4 = 5+7*4 = 33

**Math**

actual increase: 9.68-9.57 = 0.11 % increase: 0.11/9.57 = 0.01149 = 1.15%

**algebra**

15. yes 16. f(6) = 11*6+15 = 81 g(81) = -11*81^3 - 15*81^2 + 12*81 - 13 = -5,943,307 17. f(9) = 15*9^3 + 13*9^2 - 15*9 + 15 = 11,868 g(11868) = 15*11868 + 11 = 178,031 see? nothing to it! Although all the big numbers are annoying. The arithmetic just gets in the way of the ...

**algebra**

g(7) = -15*7^2 + 14*7 - 10 = -647 g(g(7)) = g(-647) = -15(-647)^2 + 14(-647) - 10 = -6,288,203 Not hard - just be careful with the arithmetic.

**help me maths anyone**

Draw a diagram. If we let T be the top of the mast O be the base of the mast P,Q be attachment points of two wires (PQ forms one side of the base of the triangle on the ground) M be the midpoint of PQ OV = 1 PV = 2 so, OP = ?3 triangle MOP is a 30-60-90 right triangle, so OP...

**@Dang**

Reiny is correct.