Solve the system 5x+3y=-9 &- 2x+y=8

Mathematics

2 answers:

kiruha [24]4 years ago

6 0

I got the same answer as you which is
X=(-3)
Y=(2)

lianna [129]4 years ago

3 0

5x+3y=-9
-2x+y=8

The first step is the trickery (and quite frankly, hardest to explain) part. You need to multiply one equation by a number that will create one variable to be the negative version of the other...(Confusing, right? Don't worry, I'll show you)

We are going to solve for X first.

We will multiply the second equation by -3
5x+3y=-9
-3(-2x+y)=(-3)8

Now simplify:
5x+3y= -9
6x-3y= -24

Now combine the two equations (add them together)
11x= -33
Divide by 11
X=-3

Now plug X in to one of the first equations:
5(-3)+3y= -9
-15+3y =-9
3Y= 6
Y= 2

So your final answer is:
x= -3
Y= 2

Hope this helps!

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A = ???? 4 −2

irinina [24]

Answer:

1. The matrix A isn't the inverse of matrix B.

2. |B|=12, |A|=12

Step-by-step explanation:

1. We want to know if matrix A is the inverse of matrix B, this means that if you do the product between B and A you have to obtain the identity matrix.

We have:

$A=\left[\begin{array}{cc}4&-2\\-1&3\end{array}\right]$

and

$B=\left[\begin{array}{cc}3&2\\1&4\end{array}\right]$

A and B are 2×2 matrices (2 rows and 2 columns), if you multiply them you have to obtain a 2×2 matrix.

Then if A is the inverse of B:

$B.A=I$

Where,

$I=\left[\begin{array}{cc}1&0\\0&1\end{array}\right]$

Observation:

If you have two matrices:

$A=\left[\begin{array}{cc}a&b\\c&d\end{array}\right]\\and\\B=\left[\begin{array}{cc}e&f\\g&h\end{array}\right]\\\\\\A.B=\left[\begin{array}{cc}(a.e+b.g)&(a.f+b.h)\\(c.e+d.g)&(c.f+d.h)\end{array}\right]$

Now:

$B.A=\left[\begin{array}{cc}3&2\\1&4\end{array}\right].\left[\begin{array}{cc}4&-2\\-1&3\end{array}\right]\\\\\\B.A=\left[\begin{array}{cc}4.3+(-2).1&4.2+(-2).4\\(-1).3+3.1&(-1).2+3.4\end{array}\right]\\\\\\B.A=\left[\begin{array}{cc}12-2&8-8\\-3+3&-2+12\end{array}\right]\\\\\\B.A=\left[\begin{array}{cc}10&0\\0&10\end{array}\right]$