Answer
$- \sqrt 2 $
Work Step by Step
$4 \sqrt 50 - 7 \sqrt 18 $
We rewrite the $\sqrt 50$ as $\sqrt (25 \times 2)$ because 25 and 2 are the factors of 50.
We rewrite the $\sqrt 18$ as $\sqrt (9 \times 2)$ because 9 and 2 are the factors of 18.
$4 \sqrt (25 \times 2) - 7 \sqrt (9 \times 2) $
*** Take the square root of 25 which is 5. Because 5 x 5 = 25
*** Take the square root of 9 which is 3. Because 3 x 3 = 9
$4 (5) \sqrt 2) - 7 (3) \sqrt 2$
$20 \sqrt 2) - 21 \sqrt 2$
The $\sqrt 2$ is common so we factor it out
$\sqrt 2 (20-21) $
We subtract 20 and 21 and get -1.
$\sqrt 2 (-1) $
$-\sqrt 2 $
