expand by multiplying <span><span>√<span>7x</span></span>⋅<span>√x</span></span> and <span><span>√<span>7x</span></span>⋅7<span>√7</span></span>
<span><span>√<span>7x</span></span><span>(<span>√x</span>−7<span>√7</span>)</span>=<span>√<span>7x</span></span>⋅<span>√x</span>−<span>√<span>7x</span></span>⋅7<span>√7</span></span>
<span>You can make√<span>7x</span></span> into <span><span>√7</span>⋅<span>√x</span></span>
<span><span>=<span>√7</span>⋅<span><span>√x</span>⋅<span>√x</span></span>−<span>√7</span>⋅<span>√x</span>⋅7⋅<span>√7</span></span><span>=<span>√7</span>⋅<span><span>(<span>√x</span>)</span>2</span>−<span><span>(<span>√7</span>)</span>2</span>⋅<span>√x</span>⋅7</span></span>
since squaring and square roots are opposite, they cancel
<span><span>=<span>√7</span>⋅x−7⋅<span>√x</span>⋅7</span>=x√7−49√x
I hope the square root symbols worked. I had to copy and paste from word. Hopefully this is what you needed!
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