Question

Find the value of a and b using substitution method:
$4a+b=3$ and $5a+2b=12$

• A. -2 and 1
• B. -2 and 11
• C. -2 and -11
• D. 2 and -11

Answer 1

Answer: (B)

-2 and 11

$4a+b=3$ ------- (1)
$5a+2b=12$------ (2)
From equation 1:
$b=34a$
Substitute the value of b in equation 2:
$5a+2b=12$
$5a+2\left(34a\right)=12$
$5a+68a=12$
$-3a=126$
$-3a=6$
$a=-2$
Now, Substitute $a=-2$ in equation 1:
$4a+b=3$
$4x-2+b=3$
$-8+b=3$
$b=8+3=11$
Therefore the solution is: $a=-2$ and $b=11$