a)
M=7/(√3-√2)-7√3-6√2
=7/(√3-√2)-7√3(√3-√2)/(√3-√2)-6√2(√3-√2)/(√3-√2)
=(7-21+7√6-6√6+12)/(√3-√2)
=(-2+√6)/(√3-√2)
=√2(√3-√2)/(√3-√2)
=√2
b)
N=(√x+1)/(√x-2)+(2√x)/(√x+2) -(5√x+2)/(x-4)
=(√x+1)(√x+2)+(2√x)(√x-2)-(5√x+2)/(x-4)
=(x+3√x +2+2x-4√x-5√x-2)/(x-4)
=(3x-6√x)/(x-4)