SOLUTION: Hi, I asked a question on this set of equations a little while ago, but was wondering, could one use Cramers Rule to solve the following .. a*4 + b*2 + c*9 + d * 7 = 21 a* 2 +

SOLUTION: Hi, I asked a question on this set of equations a little while ago, but was wondering, could one use Cramers Rule to solve the following .. a4 + b2 + c9 + d 7 = 21 a* 2 +

Question 4221: Hi, I asked a question on this set of equations a little while ago, but was wondering, could one use Cramers Rule to solve the following ..
a*4 + b*2 + c*9 + d * 7 = 21
a* 2 + b*5 + c*4 + d*4 = 11.5
a*6 + b*3 + c*5 + d*3 = 15.5
a * 8 + b * 4 + c * 6 + d * 6 = 22
If so, I would be most grateful if someone could show me how ... or get me started anyway :)
And could a general 'formula' be created using this rule to solve other similar sets of equations?
Answer by longjonsilver(2297) (Show Source): You can put this solution on YOUR website!
are your terms all powers? or is a*4 really 4a etc?

if they are coefficients then:

Now, the trouble is working out a 4x4 determinant. I do not have the time to walk though or type this here, so i advise you look on the web for a step-by-step guide to 4x4 matrices.

Anyway, Cramer's rule - ideal for this question.

work out the determinant, D for

then work out the determinant, Da for

Then do the same for Db, Dc and Dd -->

If you are still sane, then:

a = Da/D
b = Db/D
c = Dc/D
d = Dd/D

jon
RELATED QUESTIONS
Question 4221: Hi, I asked a question on this set of equations a little while ago, but... (answered by longjonsilver)

I asked this a little while ago but wrote it wrong, it's to be (1/4+/12)*1/3 = (answered by Fombitz,richwmiller)

hi again i was wondering when your writing an equation in slope intercept form and your... (answered by stanbon)

solve using cramer's rule: 4x-3y=-7 3x-9y=15 x=?, y=? i put these equations in the... (answered by Alan3354)

Hi, I play a game on my itouch that involes this math problem, and Ive done these... (answered by scott8148)

Hi, I'm working on Systems of Equations and I'm trying to solve this problem: 2x+3y=5... (answered by jim_thompson5910)

Hi everyone. I am having a little problem with word problems for my math class I was... (answered by stanbon)

i need to solve these two systems of equations: 3x+4y=12 and 2x+y=13 we have to solve... (answered by stanbon)

Hi! So, in my geometry class we are learning about special right triangles. (30,60,90 (answered by josgarithmetic,ikleyn,MathTherapy)