Thread: Help me please

1. Help me please

I have three problems I am stuck on and can't figure them out.
The first deals with functions and the book comes up with the answer of 1 but I think i am losing my hair now trying to get that.

f(3)+g(3)

the next one is solving the variables by using the addition method
3x-4y+4z=7
x-y-2z=2
2x-3y+6z=5

the next is using cramer's rule

3x=7y+1
2x=3y-1

2. Originally Posted by kbryant05
I have three problems I am stuck on and can't figure them out.
The first deals with functions and the book comes up with the answer of 1 but I think i am losing my hair now trying to get that.

f(3)+g(3)
You need to specify which functions you have.

Originally Posted by kbryant05
the next is using cramer's rule

3x=7y+1
2x=3y-1
Rewrite as,
$\left\{ \begin{array}{c}3x-7y=1\\2x-3y=-1$
Then the determinant is,
$D=
\left| \begin{array}{cc} 3&-7\\ 2&-3 \end{array}\right|
$
= $-9+14=5$
With,
$D_x=
\left| \begin{array}{cc}
1&-7\\
-1&-3
\end{array} \right|$
= $-3-7=-10$.

And,
$D_y=
\left| \begin{array}{cc}
3&1\\
2&-1
\end{array} \right|$
= $-3-2=-5$.

Thus, you have
$x=\frac{D_x}{D}=\frac{-10}{5}=-2$
$y=\frac{D_y}{D}=\frac{-5}{5}=-1$