Question
If $7(3 - 4x) = 1,$ evaluate $2x^2 + 7x + 6$
✓
Answer
$7(3-4 x)=1$
$\Rightarrow 21-28 x=1$
$\Rightarrow 20=28 x$
$\Rightarrow x=\frac{20}{28}$
$\Rightarrow x=\frac{5}{7}$
$2 x^2+7 x+6$
$=2\left(\frac{5}{7}\right)^2+7\left(\frac{5}{7}\right)+6$
$=2\left(\frac{25}{49}\right)+7\left(\frac{5}{7}\right)+6$
$=\frac{50}{49}+5+6$
$=\frac{50}{49}+11$
$=\frac{50+539}{49}$
$=\frac{589}{49} .$
$\Rightarrow 21-28 x=1$
$\Rightarrow 20=28 x$
$\Rightarrow x=\frac{20}{28}$
$\Rightarrow x=\frac{5}{7}$
$2 x^2+7 x+6$
$=2\left(\frac{5}{7}\right)^2+7\left(\frac{5}{7}\right)+6$
$=2\left(\frac{25}{49}\right)+7\left(\frac{5}{7}\right)+6$
$=\frac{50}{49}+5+6$
$=\frac{50}{49}+11$
$=\frac{50+539}{49}$
$=\frac{589}{49} .$
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