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by Alfred
Sun Jun 28, 2015 4:52 pm
Forum: Intermediate Algebra
Topic: Two equations with two unknowns
Replies: 2
Views: 148

Re: Two equations with two unknowns

Start with criss-cross multiplication.
by Alfred
Mon Apr 20, 2015 1:45 pm
Forum: Pre-Algebra
Topic: Payment formula
Replies: 2
Views: 812

Re: Payment formula

Using 200,000 borrowed, over 25 years, rate 6% annual compounded monthly P = Payment (?) A = Amount borrowed (200000) n = number of payments (25 * 12 = 300) i = periodic (monthly) interest rate (.06/12 = .005) Formula: Let v = 1 / (1 + i)^n P = Ai / (1 - v) v = 1 / 1.005^300 = .22396.... P = 200000(...
by Alfred
Tue Mar 25, 2014 10:52 am
Forum: Intermediate Algebra
Topic: Arch Problem
Replies: 2
Views: 1004

Re: Arch Problem

No graph paper?
by Alfred
Mon Mar 17, 2014 5:27 am
Forum: Advanced Algebra ("pre-calculus")
Topic: Logarithm equation
Replies: 5
Views: 1598

Re: Logarithm equation

JC531 wrote:log5(x-1)

Did you know that equals log(x-1) / log(5) ?
by Alfred
Sun Mar 16, 2014 7:31 pm
Forum: Geometry
Topic: Parabola equation
Replies: 2
Views: 7341

Re: Parabola equation

I didn't times it all out, but I got y = [(e-v)/(d-u)^2](x-u)^2 + v I think mine probably ends up like yours if you do all the steps. (Do you have to do all that?) Ok, but a parabola equation is of this format: y = Ax2 + Bx + C I really should have made mine clearer: y = Ax^2 + Bx + C where: A = (e...
by Alfred
Sun Mar 16, 2014 4:53 am
Forum: Geometry
Topic: Parabola equation
Replies: 2
Views: 7341

Parabola equation

GIVEN:
coordinates of vertex: (u,v)
coordinates of a point on parabola: (d,e)

Find equation of parabola

I got:
y = [(e - v) / (d^2 + u^2 - 2du)]x^2 - (2au)x + au^2 + v

Can someone confirm? Thank you.
by Alfred
Sat Mar 15, 2014 4:50 pm
Forum: News
Topic: Ranks?
Replies: 4
Views: 15480

Re: Ranks?

Any reasons why this forum is so inactive?

I joined yesterday, and there's been no posts since.
And most "last posts" in categories are earlier than 2014.

Kind of disappointing, given all the wonderful lessons available here...

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