Solve 3-{left(2/7{left(sqrt{21}right)}^right)}^2

$$3- { \left( \frac{ 2 }{ 7 } { \left( \sqrt{ 21 } \right) }^{ } \right) }^{ 2 }$$

Evaluate

$$\frac{9}{7}\approx 1.285714286$$

Solution Steps

Calculate \sqrt{21} to the power of 1 and get \sqrt{21}.

$$3-\left(\frac{2}{7}\sqrt{21}\right)^{2}$$

Expand \left(\frac{2}{7}\sqrt{21}\right)^{2}.

$$3-\left(\frac{2}{7}\right)^{2}\left(\sqrt{21}\right)^{2}$$

Calculate \frac{2}{7} to the power of 2 and get \frac{4}{49}.

$$3-\frac{4}{49}\left(\sqrt{21}\right)^{2}$$

The square of \sqrt{21} is 21.

$$3-\frac{4}{49}\times 21$$

Multiply \frac{4}{49} and 21 to get \frac{12}{7}.

$$3-\frac{12}{7}$$

Subtract \frac{12}{7} from 3 to get \frac{9}{7}.

$$\frac{9}{7}$$

Factor

$$\frac{3 ^ {2}}{7} = 1\frac{2}{7} = 1.2857142857142858$$