in my math book I'm stuck on this algebra question  12r -25 = 4r+7 = ? 

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cosinusix's profile pic

cosinusix | College Teacher | (Level 3) Assistant Educator

Posted on

calling the variable r doesn't necessary implies that r is a radial polar.

It could be the number of racoons ;-)

jgeertz's profile pic

jgeertz | College Teacher | (Level 1) Associate Educator

Posted on

Indeed the answer is r=4 but to offer further explanation, this is a polar equation where r is the radial coordinate otherwise known as the radius. The equation is that of a circle centered at the origin where r = the radius which is 4.

cosinusix's profile pic

cosinusix | College Teacher | (Level 3) Assistant Educator

Posted on

it is a linear equation.

You may substract 4r on both sides of the equality so that r will appear only on one side.

The equation becomes

`12r-25-4r=4r+7-4r`

if we collect like terms
` 12r-4r=8r`

`8r-25=7`

Add 25 on both side of the equation so that all the constant terms will be on one side.

`8r-25+25=7+25`

Collect like terms

`8r=32`

Divide you equation by 8

`r=32/8=4`

Answer r=4

 

Sources:
hala718's profile pic

hala718 | High School Teacher | (Level 1) Educator Emeritus

Posted on

12r - 25 = 4r + 7

We need to solve for r.

Then we will combine terms with r on the left side.

==> 12r - 4r = 7 + 25

==> 8r  = 32

Now we will divide by 8.

==> r= 32/8 = 4

==> r= 4

Then, the answer for the equation is r= 4.

jess1999's profile pic

jess1999 | Student, Grade 9 | (Level 1) Valedictorian

Posted on

12r - 25 = 4r + 7

First, subtract 4r on both sides and add 25 on both sides

By doing that, you should get

8r = 32 now divide both sides by 8

By dividing, you should get 8 on both sides

R = 4 which is your answer

atyourservice's profile pic

atyourservice | Student, Grade 11 | (Level 3) Valedictorian

Posted on

12r - 25 = 4r + 7

move like terms to the same side:

12r - 4r = 7 + 25

simplify:

8r = 32

divide by 8

r = 4

wendi111's profile pic

wendi111 | Student, Grade 9 | eNotes Newbie

Posted on

You add the 4r to the 12r and you subtract the 7 from the -25. You get 8r=32. You divide by 8 on both sides. 32 divided by 8 is 4. r=4

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