Solve the system of linear equations using linear combination.

3a + 6b = 45

2a – 2b = –12

which is the solution to the system?

ANSWER

(1,7)

EXPLANATION

The given equations are:

1st: 3a + 6b = 45

and

2nd:2a – 2b = –12

Multiply the second equation by 3,

3rd: 6a – 6b = –36

Add the first and third equations.

6a+3a+6b-6b=45+-36

Simplify,

9a=9

a=1

Put a=1 in the second equation:

2(1) – 2b = –12

-2b=-12-2

-2b=-14

b=7

because linear equations are a lot simpler than quadratics equations, and linear equations formula is a lot easier to memorize. that's why i think they're harder.

see explanation

step-by-step explanation:

a

(6r + 7) + (13 + 7r) ( remove brackets and collect like terms )

= 6r + 7 + 13 + 7r

= 13r + 20

b

remove brackets and collect like terms

13 - r - 1 + r

= 12 - r

c

remove brackets and collect like terms

= - 8 - r + 2r - 4

= - 12 + r

d

remove brackets and collect like terms

= 7r - - - 6r

[-   - = - - = - ]

= r -