Question

For each expression, select all equivalent expressions from the list. 20x 2x+ 2.9 (a) 2x + 18 O2(9x+1) O2(x+9) 11y+9y 9+11y 11y+9 (b) 13+10y-2-y 9y+11

Answer 1

SOLUTION

(a)

$\begin{gathered} 2x+18=2\times x+9\times2 \\ =2\text{ . }x+9\text{ . 2} \end{gathered}$

Also

$\begin{gathered} 2(x+9) \\ =2\times x+2\times9 \\ =2x+18 \end{gathered}$

But

$\begin{gathered} 2(9x+1) \\ =18x+1 \\ \text{and } \\ 2x+18\text{ can't be added so it is not equal to }20x \end{gathered}$

Hence only the first and second options are correct

(b)

$\begin{gathered} 13+10y-2-y \\ \text{collecting like terms we have } \\ 13-2+10y-y \\ 11+9y \\ =9y+11 \end{gathered}$

Hence only the last option is correct