Question

Use the FOIL method to evaluate the expression:

Answer 1

Answer:

$\sf b.) \ 1 +2\sqrt{7}$

Explanation:

Foil method: (a + b)(c + d) = ac + ad + bc + bd

Solving steps:

$(4 - \sqrt{7} )(2 + \sqrt{7} )$

$(4)(2) + 4(\sqrt{7} ) + (-\sqrt{7} )(2) + (-\sqrt{7} )(\sqrt{7} )$

$8 + 4\sqrt{7} - 2\sqrt{7} - 7$

$8 -7 + 4\sqrt{7} - 2\sqrt{7}$

$1 +2\sqrt{7}$

Answer 2

option b) 1 + 2√7

Step-by-step explanation:

Foil property method :-

$\red{ \boxed{ \orange{ \rm (a + b)(c + d) = ac + ad + bc + bd}}}$

then, on substituting the values,

$\sf⇒ \: \: 8 + 4 \sqrt{7} - 2 \sqrt{7} - 7$

$\sf⇒ \: \: \green{ \underline{\bold{ \red{1 + 2 \sqrt{7} }}}}$