# Homework Help: Pre Calc, how to you solve an equation if it says a≠0? please help!

1. Sep 11, 2010

### tintin1234

it says "use the inverses found in Problems 29-38 to solve each system of equations"(not sure what it means by that)
pg742,#47)
2x+y= -3
ax+ay=-a
a≠0 <----a≠0 was already in the book next to the equation
the book says the answer is x=-2,y=1
-what i have so far-
[2 1] [-3] --> (2 x a)-(a x 1) = 1a
[a a]=[-a]
[a -1]
A^-1= 1/det(A) x [-a 2]

[a -1] [1 -1/a]
A^-1= 1/1a x [-a 2] = [-1 2/a] <---inverse

[x] [1 -1/a] [-3]
[y] = [-1 2/a] [-a]

50) bx+3y= 14
bx+2y=10
b≠0 <------b≠0 was already in the book next to the equation

My math book is called "Precalculus seventh edition Sullivan", its a dark green/blue color(just in case you might have it). on pg 742 it says "show that each matrix has no inverse"

2. Sep 11, 2010

### Staff: Mentor

Everything looks fine, so far. What do you get for x and y when you do the matrix multiplication on the right?
Do the same thing you did in the previous problem to find the solution for this problem.