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3X-4Y=-15 5X+Y=-2 ------------------------------------- Y=-5X-2 3X-4(-5X-2)=-15 3X+20X+8=-15
23X=-23
X=-1
3(-1)-4Y=-15 -3-4Y=-15
-4Y=-12
Y=3
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TO
SOLVE THIS PROBLEM YOU NEED TO FIRST SOLVE FOR Y AND THEN PLACE THE
Y VALUE IN TO THE PLACE OF ALL THE LETTER Ys.
SOLVE FOR X. AFTER YOU SOLVE FOR X PLACE THE VALUE OF X IN TO THE PROBLEM IN PLACE OF THE LETTER X. ONCE YOU HAVE SOLVED FOR BOTH
X AND Y CHECK THE PROBLEM BY PLACING THE VALUES FOR X AND Y INTO THE ORIGINAL
PROBLEM.
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X+2Y=6
(X+2Y=6)=-2
-2X-4Y=-12
2Y=-2 Y=-1
X+2Y=6 X+2(-1)=6 X+-2=6
X=8
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TO
SOLVE THIS PROBLEM FIRST YOU NEED TO MAKE SURE THE PROBLEM IS SET UP IN
THE WAY TO THE RIGHT (WHERE X AND Y ARE ON ONE SIDE OF THE EQUALS SIGN
AND THE OTHER NUMBER IS ON THE OTHER SIDE OF THE EQUALS SIGN)
MULTIPLY THE WHOLE PROBLEM TO THAT YOU CAN GET RID OF A VARIABLE. ADD BOTH PARTS OF THE NEW PROBLEM TOGETHER AND SOLVE FOR THE FIRST VARIABLE. _________________________ SOLVE FOR THE SECOND VARIABLE. PLACE THE VALUE YOU GOT FOR THE FIRST VARIABLE INTO THE PROBLEM AND THEN WORK THE PROBLEM OUT TO GET THE VALUE FOR THE SECOND VARIABLE. CHECK YOUR WORK. |
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| THE SUM OF
A CERTAIN NUMBER AND A SECOND NUMBER EQUALS 42. THE FIRST NUMBER
MINUS THE SECOND NUMBER EQUALS 52. FIND THE NUMBER.
_____________________________ X-Y=52
2X=84
X+Y=42 47+Y=42
Y=-5 _____________________________
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To
solve this problem first you must find all of the equations needed to solve
it. Then once you have found the equations the equations need to
be set up to be solved. Use the same method as you did for the linear
combination problem.
Once you
have the value of one of the variables place the value into the problem
to solve for the other variable.
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