Weird answer for "Solving systems of linear equations" in SAT math section – Khan Academy - Centro de ayuda

¿Cómo podemos ayudar?

vchamp44

26 de febrero de 2018 22:34
Editado

0

This was the math problem.

1.5a - 4.5b = 3(a + b)

5.5b = 5(b - a) + 2.5a

Consider the system of equations above. If (a,b) is the solution to the system, then what is the value of b - a?

This is the solution Khan Academy gave.

A part of the solution confused me. I understood how they reached 5.5b = 30b - 12.5b, but I don't understand how b = 0. Shouldn't b = 12?

Nueva publicación

2 comentarios

Iksha Handa

27 de febrero de 2018 04:00
3

Acciones de comentarios Permalink
So after 5.5b = 30b -12.5b the equation simplifies to

5.5b = 17.5b

-17.5b = -17.5b Then bringing the 'b's to one side you have

-12b = 0

or alternatively 0 = 12b (by subtracting 5.5b from both sides)

0 divided by any number is 0 so b = 0
vchamp44

28 de febrero de 2018 16:09
0

Acciones de comentarios Permalink
Gotcha. So were dividing both sides by -12. I thought we were adding +12 to both sides to get b = 12.

La publicación no admite más comentarios.